John Gore’s telescope

CAROLYN FORSTER: Welcome to the first curator’s talk for 2008. It’s lovely to see so many of you here. I’m Carolyn Forster and I’m president of the Friends. This is a very successful series for us. We’re delighted that Michelle is here this afternoon to talk to us about John Gore’s telescope. I was going to say a little bit, but Michelle will be able to tell you a lot better than I can anything about this subject. Michelle has been with us for quite some while now -

MICHELLE HETHERINGTON: Three years.

CAROLYN FORSTER: It was wonderful that you came across from the Library.

MICHELLE HETHERINGTON: I think so.

CAROLYN FORSTER: We are delighted that you are here with us. Michelle, thank you so much for speaking to the Friends today.

MICHELLE: Thank you, Carolyn, and thank you also to the Friends for making this opportunity available for curators to come and talk to some of our great supporters. It’s my pleasure today to talk to you about a very beautiful and significant object - I use the word ‘object’ in a slightly elastic sense - that entered the National Museum’s collections officially in 2006.

This is John Gore’s telescope. As you can see, there are two eyepieces, a lens and a lens cap, and the original mahogany tube and the leather coating that used to keep it all together and a few other bits and pieces. And on display, our lovely conservators have brought some of the more robust pieces for you to have a look at more closely.

This is the condition the telescope was in when it came to the Museum [shows image]. It was the gift of John Galloway, who lives in Queensland, and who is the great-great-great grandson of John Gore who entered the navy in about the 1750s and ended up becoming a captain and had a major role to play in two of Cook’s Pacific voyages.

This is Captain Gore [shows image]. Obviously being at sea for a long period of time in the eighteenth century didn’t improve your looks. But I’m sure his family loved him. The painting is by John Webber, who was the artist on Cook’s third voyage, and was created in about 1780 [shows image]. It would have been painted in part to create an image of Gore that could then be engraved for use in the official published account of the third voyage. But more of Captain Gore later.

Here we see one of the long eyepieces. This is the night-and-day eyepiece; this is the day-only eyepiece; and this is the little metal sleeve that is at the eye end of the telescope. Here is the engraving that is on the night-and-day eyepiece: ‘Dollond London, Day or Night.’ That tells us it is an astronomical telescope and that it was made by the famous family of London opticians, Dollond - sometimes referred to as the House of Dollond.

And here is Peter Dollond’s trade card [shows image]. His shop was at the sign of The Golden Spectacles and Quadrant. We can see examples of the sorts of materials that he supplied to the London populace [shows image]. In this top corner we’ve got one of those little pocket globes, which now sell for considerable sums on the market, and we also have an eyepiece on the other top corner next to a sundial. And within the image itself, we’ve got a quadrant, the telescope, a microscope, and spectacles.

The House of Dollond began in about 1750 when Peter Dollond set himself up as a spectacle maker and basic optician. There was a huge market in London for optical instruments amongst the scientifically literate, which was a more extensive group than we might consider. In the 1700s you did not need a ‘proper’ university-based scientific education, as you do these days, to be considered a scientist. You just needed to have the money to pursue your interest and access to books, many of which were written in Latin and Greek, although fortunately for the British, mathematical textbooks were increasingly produced in English. And if you were a gentleman and had scientific interests, you could become a member of the Royal Society provided your name was put forward and you were approved by the Fellows.

Within this group in society there was a great deal of ‘amateur’ practice of science. They didn’t see why they shouldn’t have a telescope, why they shouldn’t use all the equipment that was becoming available so that they too could look at astronomical events as they happened. In the mid-eighteenth century London was becoming one of the major centres for quality scientific and navigational instruments, and opticians and makers of optical and scientific instruments were flourishing.

Peter Dollond was the grandson of a Huguenot weaver. His father John had followed his father into the silk-weaving industry in London, but his great passion was science. John could read Latin and Greek, he’d studied mathematics and was in an excellent position to excel as an optician. So, two years after Peter sets up his business, his father John joined him and began work on one of the basic problems which limited the effectiveness of telescopes. And this is the point at which we begin a crash course in optics. I hope you’ll all bear with me.

This is a convex lens - before I begin on this I should say that, in 1608, Hans Lippershey, who was a Dutch optician, invented the telescope. There is considerable evidence to suggest that it was one of those discoveries that was about to happen in multiple places around Europe. So there were a number of other opticians and scientists who were working on the idea, but it’s Hans Lippershey who gets his name attached to the development.

Within a year, 1609, Galileo Galilee had heard of this fantastic new instrument, had made one and was pointing it at the sky. (Apparently, nobody had thought about that in the preceding year.) He quickly discovered the craters on the moon, sunspots, four of the satellites for Jupiter and the phases of Venus. And this was with a telescope that had a field of vision as wide as a piece of spaghetti held at arm’s length. It’s amazing that he managed to do it.

In 1611, the problem with the narrow field-of-view width was solved to an extent by [Johannes] Kepler, who created a telescope using two convex lenses, one at the objective - that’s the big, round end - and one at the eyepiece end. However, Kepler’s telescope did not solve the major problem with telescopes, which results from the way light refracts. Light going through a plain sheet of glass in a straight direction will continue in a straight direction as it comes out the other side. But if it hits the glass at an angle, it will refract, which means it will break up into its constituent parts, because of course white light is composed of the colour spectrum. That’s going to cause a few problems because light passes through air at a certain speed, but when it passes through glass it travels at a speed one and a half times slower. That is called the index of refraction, which is about 1.5 for most types of ordinary glass.

In this example you’ve got a convex lens [shows image] and as the light hits one face of the lens it bends and then, as it comes out of the lens, it bends a second time. So you’ve got the light bending and refracting. There’s a problem with that because the different wave lengths of light travel at slightly different speeds, and the blue at one end travels slightly faster than the red at the other. The point of best focus, as shown on this image, is actually the green wave length and, not surprisingly, the human eye is happiest with the green wave length. What happens is that, as the light comes out of the lens, the blue part of the spectrum focuses first, then you get to the green spectrum, which is the bit we’re happiest looking at, and then the red spectrum focuses. So what you end up with at the point of focus is a lovely little clear spot, but it is surrounded by a blurry haze of the colour purple.

So, the scientifically inclined now had telescopes through which, despite their smallish field of vision, they could still see amazing things. But they also had what’s called chromatic aberration. That is the name for what causes the purple ring. It seriously compromises the amount of detail that you can see. They tried very hard to fix this problem and they discovered that, the longer the length of the telescope, the less noticeable the chromatic aberration. But when telescopes reached a length of 150 feet and still had chromatic aberration, they had reached an impasse. There comes a point at which you can no longer aim a very long telescope accurately, and many people applied themselves to solving the problem. Even [Isaac] Newton spent considerable time trying to work out a way of dealing with chromatic aberration, and ended up publishing his opinion that it could not be solved; he felt it was inherent in the nature of glass lenses.

Then in about 1731 a gentleman called Chester Moore Hall was doing a small experiment and decided that, if you had a glass lens of two different refractabilities, or refraction indexes, you could cause the way the light is bent to correct itself as it passes through the glass. What we see here is a flint glass lens - that’s the one with one flat surface - and nestled into its concave surface is a convex lens made of crown glass.

By the way, Newton didn’t just give up. He invented the reflecting telescope, which entirely does away with chromatic aberration and uses a curved mirror to bend the light within the telescope. The only problem was that, at the time he invented this, they couldn’t make a sufficiently smooth curved mirror for it to work as well as it does nowadays.

Chester Moore Hall, who was an amateur, a gentleman of science, sent off his instructions for grinding the flint glass lens and the crown glass lens to two separate opticians in London. And unfortunately for him, those two opticians sent the orders to a third gentleman, Mr George Bass, who, receiving these two orders at much the same time, worked out that they were for the same person, put the resulting lenses together and discovered that here was the answer to chromatic aberration. As we can see, the light comes through the flint lens, and the blue and the red wavelengths are bent and then bent back again by the Crown glass lens, so that they both focus at exactly the same point.

This is the lens from the Gore telescope [shows image] and, as you can see, the lens itself has been broken. But what that allows us to see is that it is an achromatic lens: it has a flint lens and a crown lens placed together.

And fortunately, we have with us today Herman Wehner, an astronomer who’s been involved with the Stromlo Observatory in Canberra. Herman, who has been looking at the Gore telescope lens, tells us that there is a special glue that we can use to put the lens back together again, which will be fantastic. But how did Dolland create an achromatic lens? Chester Moore Hall, after he had discovered how to make an achromatic lens, did nothing with it. He just left it in his drawer and the solution lapsed for more than 20 years.

In 1758 John Dollond published a paper in the Philosophical Transactions of the Royal Society - he was not at that point a member, so his paper had to be put forward by somebody who was - outlining how to make an achromatic lens, a lens that did away with chromatic aberration. For his pains, he was made a Fellow of the Royal Society. He won the Copley Medal, which was the major prize issued by the Royal Society for the best piece of scientific discovery in the year, and he was appointed the King’s optician. He was also given a patent for his discovery, which he apparently had no great desire to pursue the protection of. His son Peter had a very different outlook.

This is what the telescope may have looked like when it was first put together [shows image]. I don’t think you’ll be able to read all of those details, but I’m hoping we can use this image, published by Dolland London, to help us with the reconstruction of the telescope, for that is our aim. Our aim is to put the telescope back together again the way it was. We’re not going to renovate it particularly, but we are going to turn it back into a usable telescope. It will then go on display in the Australian Journeys gallery, which is currently being redeveloped and opens late in 2008.

John Dollond only lived till 1761. He enjoyed the benefits of his extraordinary work on lenses for a little more than two years, and died as his son Peter was beginning to pursue anyone infringing his copyright or his patent. There was a lot of anger amongst the opticians of London, 35 of whom signed a petition against Peter Dollond saying, ‘Chester Moore Hall invented the achromatic lens a good 30 years ago. Why should Dollond have this patent?’ It went to court and, in the end, the judge decided that it was not the person who made the discovery but then kept it ‘locked in his escritoire’, but the person who made it available to everybody else who should have the benefit of the discovery.

This is a picture of the Royal Observatory near Greenwich painted in 1682, not long after it was established by Charles II [shows image]. I’m showing you this because one of the reasons why the achromatic telescope was such a fantastic discovery and why the British were so pleased that the problem had been solved at last, was that, as a maritime nation, most of Britain’s military encounters took place at sea. They were able to put most of their money, most of their defence budget, into the navy because, unlike most of their rivals in Europe, they did not have to maintain a large standing army to guard their borders. The sea did that for them very well.

There was, however, a major problem associated with the navy at that time, and that was the difficulty of working out where, exactly, your ships were. This was the problem of accurately determining longitude. I’m sure many of you will have read Dava Sobel’s excellent and entertaining book on the discovery of an effective method for calculating longitude, so I won’t go into it at great length here. But in order to solve this problem the British state, the Crown, had instituted a Royal Observatory and the post of Astronomer Royal, which at this point was held by Dr Nevil Maskelyne. It was part of an unusually well-organised official program aimed at improving navigational science. In this, the British were decades ahead of their European rivals.

And now back to John Gore. John Gore is thought to have been a native of Britain’s American Colonies. We think he might have been born in about 1729-30 in Virginia, and he came to England quite early on in his young adult life. We still need to find out much more about John Gore. Al Gore is a relative of his, and also Gore Vidal. The Gore family has prospered over the years.

Joining the Royal Navy in the 1750s, as John Gore did, was an excellent way of advancing quickly through the ranks, because Britain was about to become fully involved in what is known as the Seven Years War from 1756 to 1763. The peace settlement for this war reallocated the colonial possessions of European powers: France largely lost her toehold in Canada and her toehold in India; Spain was no longer in a position to insist on what she saw as her exclusive rights over the Pacific; and Britain emerged with more colonies and unfettered access to the Pacific.

Shortly after the ink dried on the Treaty of Paris, the British set off for the Pacific in 1764 with [Commodore] Byron on the Dolphin, and he carried with him, as master’s mate, the young John Gore. They don’t find very much: a lot of water, not a lot of land. It wasn’t a great success. They’d only been back three months in 1766 when the Dolphin was sent off again, this time with Samuel Wallis as the captain. The Dolphin’s second voyage was only marginally more successful, and that success lay in the discovery of Tahiti, which they called King George’s Island.

Fortunately, the purser [accountant] on board this ship had been trained by Nevil Maskelyne to calculate longitude. All the techniques for establishing longitude involve being able to calculate the time at the port from which you sailed and the time at the place that you have reached, because each hour represents 15 degrees of longitude. Of course clocks at this point were not able to work reliably at sea, and all sorts of bizarre methods to establish the difference in time compared to the home port were suggested. Such as injuring a dog in London at a set time so that the dog you carried on your ship would howl with pain in sympathy. Such methods hadn’t worked. What had worked was a method of calculating lunar distances perfected by Tobias Mayer, a German mathematician.

The lunar distance method uses the movement of the moon relative to the sun and the stars as a way of telling the time. The altitude of the moon and a particular star, and the angle between then is measured and the resulting figure is checked in a set of tables - the nautical almanac - to find out what time in Greenwich it equates to. The complicated mathematics required for the calculation took about three hours. But as I say, the purser knew how to perform the calculations. He was able to calculate the longitude and latitude of Tahiti, which meant that the island could be found again. In the past, European voyagers had discovered islands in the Pacific, but their calculations of position were unreliable and their discoveries could not be found again.

And when the Dolphin arrived back in England, shortly before HMB Endeavour was due to sail to the South Seas, they were able to give the location of a richly supplied island from which to observe the transit of Venus - the ostensible reason for Captain Cook’s voyage.

John Gore had sailed with Wallis on the Dolphin as well. And he spent some time during the month that the ship was at Tahiti learning the language and doing a major examination of what was going on in the interior of the island. The report he wrote on what he found was given to the Admiralty, and he also told them that he was sure he had seen the Great South Land, just on the horizon. This excited the British government because they were hoping to find something like the New World - the Americas - in the Pacific. That was their great wish. And that was what Cook’s secret instructions, to be opened after observing the transit of Venus, told him to find and claim for Britain.

Gore, because he’s a bit of an old hand at Pacific voyages and speaks the language in Tahiti, is selected to go on Cook’s voyage, and they don’t actually seem to have got on terribly well. There’s a letter from Sir Charles Blagden, who was secretary to the Royal Society for many years during Banks’s presidency, reporting that [Daniel] Solander had told him that Cook didn’t really like Gore, with the suggestion that Cook felt a little uncomfortable about Gore’s superior knowledge.

Cook had previously only been in charge of crews of about 20. Now here he was with nearly 100 men under his command, and there were people on board like Gore who knew much more about the Pacific and who could speak Tahitian when he could not. He certainly sent Lieutenant Gore off to do all the negotiations with the local people that they visited. He was in charge of the watering parties, the parties sent out to get wood, the parties sent out to make contact. And Lieutenant Gore’s unshakable belief in the existence of a Great South Land resulted in some rather superior comments - I think the tone is superior on Cook’s part in his journal. Banks, I must say, shared Gore’s hopes.

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We can see here the lengths to which Cook was prepared to go to prove to people like Gore - and, of course, Banks - that the cloud that they could see on the horizon was not hiding the Great South Land. They began to call it ‘Cape Flyaway’, the sort of land that constantly disappeared or retreated in front of you the closer you got. Cook is saying here that he has spent a day and a half sailing after a bunch of cloud on the horizon just to prove to Gore that there was nothing there. And having done that, he then writes, ‘I would like to have done more work to find the Great South Land but, given that the ship wasn’t in any condition to sail east back across the Pacific, I decided to go up the coast of New Holland.’

So for those people out there who still think that Cook discovered the Great South Land, also known as Australia, he didn’t. He knew Australia was New Holland, he had a fairly good idea where it was in relation to New Zealand and he thought he’d just sail up the coast and see what was there.

This is Joseph Banks [shows image], and Joseph Banks got on terribly well with Gore, because Gore had one skill in particular that was of enormous use: he was a great shot. Unfortunately, he was also the first person to have killed a Maori with a gun during a trade altercation. But the other thing he did was he shot the first kangaroo. The kangaroo was taken back by Mr Banks, its skin was reconstituted in a fairly uncomfortable-looking position and was painted by George Stubbs, the famous eighteenth century painter of horses, amongst other things. This is the engraving of Stubbs’s painting that appears in the official account of the first voyage [shows image].

As most people will be aware, Banks intended to go on Cook’s second voyage to the Pacific which was going to search for the Great South Land. But the changes Banks had had made to the ship to ensure his personal comfort this time made the ship so unseaworthy that the crew thought it was going to turn turtle as it sailed the quiet waters of the Thames. So all of the additions were dismantled, Banks was furious and ended up withdrawing from the second voyage. And, interestingly enough, Gore did not go on the second voyage either. He went instead with Banks to Iceland, which shows that Gore knew where the best patronage lay.

For Cook’s third Pacific voyage, this time to find the North West Passage, Gore is appointed first lieutenant on the Resolution. Cook dies on the beach at Kealakekua Bay on 14 February. The anniversary is tomorrow, so next time people say ‘Happy Valentine’s Day’, think, ‘No, happy anniversary of the death of Captain Cook’. So the captain of the consort ship Discovery, Charles Clarke, became the captain of the Resolution, and Gore was made captain of the Discovery.

Both ships continued looking for a North West Passage between northern America and Russia at the top of the Pacific, hoping to find a route into the Atlantic, but their path was blocked by ice. Of course, a North West Passage may become more and more navigable as time goes on with global warming, but for the Resolution and Discovery, it was entirely un-sailable. And then poor Captain Clarke dies of TB and is buried in Russian territory, near Kamchatka.

So now Gore is the commander of the whole expedition. He manages to bring both ships home with very little further loss of life, arriving in about April 1780. However, there were such terrible storms in the English Channel that they actually sailed up around Scotland to get into the Thames, arriving months later.

What happened to Gore after his return, and how do we know that this was his telescope? These are the sorts of things that, as curators here at the National Museum, we spend a lot of our time working on; and I have written what is called an object biography for the telescope. The best evidence we have that it belonged to Gore is that it has been handed down through the family, and that’s part of its provenance. The date of the telescope we can fix between 1761, because the name ‘Dollond London’ which appears on the telescope eyepieces, is the name that Peter Dollond used for his company after his father’s death, and 1783 when drawn brass tubes began to be manufactured replacing the braised tubes found on our telescope.

So we have a period from 1761 to 1783 for the manufacture of the telescope which encompasses Gore’s career very nicely. Gore largely retired after he returned from the Pacific that fourth time, and in fact took up Cook’s now vacant position at the Greenwich Hospital. Cook had been made a captain of the Greenwich Hospital on his return from the Pacific in 1775, which gave him a pension and somewhere nice to live, as a thank you from the State. And when Cook failed to return home, his rooms were allocated to Gore.

But how would Gore, only a master’s mate in 1761, have had the money to buy a rather expensive telescope? They cost up to 12 guineas for the really big ones, and this telescope has a two and three-quarter inch objective lens, which was the biggest lens available for general purchase. [Telescopes with bigger objectives could be commissioned, but large enough glass blanks from which to grind the lenses were not always available due to the difficulty of casting glass without striations at this point.] We’re still conducting research, but I think the answer might lie in Gore’s capacity to shoot the wildlife, and his capacity to deal with the locals, which meant that he was able to come back to England with a fine collection of specimens and objects, which would have been very keenly sought after by gentlemen collectors back in London - one of whom, Banks, had become his patron. There is a suggestion that perhaps Banks gave him the telescope. Well, Banks may have, but perhaps he didn’t have to. Perhaps he had put Gore in a financial position where he was able to purchase a telescope for himself.

Gore died at Greenwich in 1790, and Banks was the executor of his will. Before heading out on the third voyage Banks had received a letter from Gore asking him to keep an eye on his son. While Gore had to be very respectful towards Banks, I think the nature of the relationship was good. That son, who was also called John Gore, grew up and joined the navy. He came to Australia with his family in 1834, and that’s how the telescope got to Australia.

Our plans for the telescope are that it will be put back together again. You have possibly noticed the two young women working here installing these objects. One of them, Prue Castles, is a conservator. It’s her role to put the telescope back together again, with advice. She’s undertaking a research project herself at the moment to try to work out what would be the best way to treat this object. Everything that comes into our collections has to be assessed and, if it requires treatment, that treatment is given to it, especially before it goes on display.

The telescope will become part of a module in the Australian Journeys gallery that examines European voyages of discovery. From my point of view, the telescope is the most fantastic object to tell part of that story because of its significance in astronomy and the contribution of astronomical readings to safer navigation, British naval power and advances in the field of navigation - which leads to the discovery of the east coast of Australia in particular and which inevitably, it seems, has led to the establishment of a British colony in Australia. And here we all are today.

QUESTION: You said that he sent the specifications for the glass to two different people. Do you mean he sent one piece to one and one to another?

MICHELLE HETHERINGTON: No. What he did was he sent instructions saying, ‘I require a crown convex lens so high, so wide and ground to these specifications.’ And to the other optician he sent one saying, ‘I require a lens made of flint glass.’ Basically, he would not have been in a position to grind the glass himself, I don’t think, although it’s possible.

QUESTION: But he sent orders for one piece to two different people?

MICHELLE HETHERINGTON: Yes, obviously hoping to keep his discovery to himself for a bit longer.

QUESTION: There was a pretty big American community in London just as there would be a large Australian one 100 years later. I’m thinking of the painters Benjamin West and John Singleton Copley. There might be papers that some of them have left and that have even been put together by American historical societies into some kind of volume, so that’s a possibility. And I guess that there are American genealogical societies that would be very interested in the Gore family and might have traced the entire family tree. But those are both just guesses.

MICHELLE HETHERINGTON: The Gore family themselves are very busily examining their own family tree, and they say they cannot find much more information about him at this point. Jo Parker was the curator here at the Museum at the time who met Mr Galloway and was involved in the acquisition of the telescope. She sent off for John Gore’s will, John Gore’s logbook and all sorts of things like that. I’m waiting for them to arrive. Soon, I hope. There are lots of sources that need to be checked, but they all involve a lot of time and a lot of reading on microfilm readers, trying to understand eighteenth century handwriting and such like. And of course there are always many other calls on our time.

But it would be fantastic to be able to find out: how did he get his hands on this? Did it improve his prospects within the navy? ‘I am a great astronomer. Look at the way I can calculate longitude.’ Of course, the whole issue with the longitude is improved with the second Cook voyage when they take the chronometers. But that first Cook voyage, using Maskelyne’s updated nautical tables, is the one where the use of the telescope would have been particularly important.

QUESTION: He could have used it just to shoot the wildlife.

MICHELLE HETHERINGTON: Well, he could have, except that an astronomical telescope will show you the image of what you are looking at upside down at this point so it might have been a bit hard to focus.

QUESTION: … Are they stuck together and, if so, what did they use?

MICHELLE HETHERINGTON: They are placed so closely together that I’m not sure that they would have needed an adhesive of any kind. They’re sort of effectively put into a frame that pushes them together, but I’ll ask about that.

CAROLYN FORSTER: Michelle, thank you for giving us such a marvelous insight into this extraordinary item, and we’ll all look forward very much to studying it in its new home later this year. Thank you once again for making this item come alive for us.

MICHELLE HETHERINGTON: My pleasure.