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watch up every day, which he carefully observed. From the foregoing remarks,

he made the following corrections.

Centre of Venus on the sun's limb at ingress

Interior contact at the ingress

Interior contact at the egress.

Centre of Venus on the sun's limb at the egress

Total egress....

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And if the same time be allowed for the first semidiameter of the

planet coming on as the other 3, it must have commenced at 8h 4m 50, so that the total duration was.

6 22 48

XCVII. A further Account of the Case of the Family at Wattisham,* in Suffolk, whose Limbs mortified. By Charlton Wollaston, M.D., F. R. S. Dated Pall Mall, Oct. 29, 1762. p. 584.

As the Society may be curious to know some further particulars relating to this singular calamity, I thought it might not be improper to acquaint them that most of the unhappy sufferers have survived it. The father is perfectly recovered; except that the two fingers, which were particularly affected, remain in some degree contracted.

The mother is still alive. In my former account I mentioned that one of her feet had separated at the ancle; and that the other leg was perfectly sphacelated to within a few inches of the knee, but not then taken off. Some little time afterwards the husband broke off the tibia, which was quite decayed, about 3 inches below the knee: the fibula was not decayed; so the surgeon sawed it off. The stumps of both legs still continue unhealed; and as the ends of the bones in both of them seem to be carious, and the woman will not consent to any further operation, they may perhaps never heal. The mortification however has not in this limb, nor indeed in any one of these cases, spread beyond the original separation. Her right arm is considerably wasted, and the fingers contracted. The eldest girl Mary died within a few weeks after I saw her. The 2d girl Elizabeth is perfectly well: the sores quite healed. The 3d girl Sarah is not yet well. Her foot separated at the articulation of the os scaphoides with the astragalus. The os calcis and astragalus are both of them carious, and probably keep the wound from healing. The 2 boys are perfectly recovered; and seem in every respect as healthy as possible.

I have taken all the pains I could to inquire into the cause of so remarkable a disorder; and Mr. Bones, the minister of the village, who knew the family before this misfortune happened to them, and has ever since been indefatigable

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in his attention and tenderness to them, has also made all the inquiry in his power: but we have not been able to find that there was any thing particular either in their diet or manner of life, to which it could be attributed. The corn with which they made their bread was certainly very bad: it was wheat, that had been cut in a rainy season, and had lain on the ground till many of the grains were black and totally decayed: but many other poor families in the same village made use of the same corn, without receiving any injury from it. One man lost the use of his arm for some time; and still imagines himself that he was afflicted with the same disorder as Downing's family: but by what I could learn from him, there seemed to be no reason for this supposition. He is long since perfectly recovered.

XCVIII. Observations on the Tides in the Island of St. Helena. By the Rev. Nevil Maskelyne, A.M., F.R.S. Dated St. Helena, Jan. 26, 1762. p. 586.

For this purpose Mr. M. had a post about 10 feet long erected in a convenient place in the harbour before James's fort, which was the properest situation that could be found, being to the leeward part of the island, where ships may ride at anchor safely all the year round. One side of it was painted black, over which white strokes were painted at the distance of 3 inches, which were marked with the figures 1, 2, 3, &c. according to the order of the strokes, reckoning upwards from the bottom. The water sunk down to about the figure O at the new and full moons. The following example of his method of making these observations may serve to give an idea of the whole. When the water sunk, he took its altitude on the post at the lowest point, and immediately as it rose again, he took it at the highest, and repeating the experiment in this manner, he at last took a mean of all the observations for the true height of the water. But the medium of the lowest and highest which immediately succeed each other seldom differed much from the medium of them all. The numbers on the post by which the altitudes were taken, are at the distance of 3 inches from each other, as before observed. > November 16, 1761, 5h 16m P.M. he took the following observations of the altitude of the water by the side of the post 11, 12; 9, 13; 10, 124; 9, 141; 9, 12; 9, 134; 10, 13; 9, 14; 9, 13; 9, 14. The medium of all is 11 for the true altitude of the water. Mr. Mason at the same time by about as many observations found 11.

Some times, when the rise and fall of the water was very quick, instead of taking the more regular rise and fall of the water, which succeed each other at longer intervals, he took notice of every the least rise and fall, in which case he had an assistant to write them down as fast as he told them. As an example of this December 2, 11h 15m A.M. by a mean of 69 observations taken in this manner, he found the altitude of the water to be 3; and at 11h 21m A. M. by

a mean of 52 observations, taken at the more regular rising and fallings of the water, he found the altitude to be 3. He always looked at his watch before he began to note the height of the water, and looked at it again when he had finished the experiment; the medium of the two times he set down as the true time of the observation. The times set down are exact to the minute.

Mr. M. says nothing with respect to any conclusions that may be drawn from the above observations, except that the greatest rise and fall of the water, observed at the sysigies of the sun and moon, is about 13 divisions of the post, or 39 inches; and that the smallest rise and fall in the quadratures, is somewhat less than 7 divisions of the post, or about 20 inches; and that the mean time of high water happens 2h 15m after the moon's passing the meridian, though in the course of every fortnight the said interval is very much varied by the different influence of the sun at different times, as the theory requires.

XCIX. Extract of a Letter from M. de la Lande, at Paris, to the Rev. Nevil Maskelyne, F. R.S. Dated Paris, Nov. 18, 1762. p. 607.


I am glad that you have proved, from your own experience, the exactness of the observations of the distance of the moon from stars for finding the longitude at sea, as M. de la Caille had done in 1753. I am as fully convinced as you can be of these advantages, and am not a little pleased to learn that you are about printing a concise method of computing the corrections of refraction and parallax. In the sector, which our members of the academy carried with them to the north, the plumb-line descends from an angle as in this figure, so that it is obliged to fall into the vertex of the angle; and it passes over a point A, with which it is made to correspond, by the help of a microscope. It is a pity that Mr. Sisson neglected so essential a circumstance in your sector, but that is not your fault. The sector, with which M. de la Caille made all his observations, and which is come into my hands since his death, has a fine needle at the centre, from which the silver wire is suspended by a loop, thus

M. Pingre, who is returned from the island of Rodrigues, has found the parallax of the sun to be the same as I have done;, namely 9". I am not surprized that you find it to be only 8′′, since the Swedish observations, which appear to me to be very good, make it still less than you have found it. These uncertainties arise from our not having the difference of the meridians of the Cape, Rodrigues, Tobolski, Paris, and London, well determined. You are therefore quite right to collect together the observations of Jupiter's satellites, which will serve to find these longitudes. I thank you for those which you have sent me, and I have hereto added those of the first satellite which were made at Paris in 1761, for one can scarcely employ any but these for this purpose.

On the 19th of July 1763 we shall have an occultation of Antares by the moon, on the 2d of November an occultation of Mars, on the 8th of September one of Mercury: they will be very proper for determining the difference of longitude between London and Paris. In 1764 there will be a still greater number. But if have an inclination to undertake a labour of this kind, you may meet you in the memoirs of the academy with occultations of stars observed at different times, and find some corresponding ones made at London, whence you may deduce the difference of the meridians of these two cities, which we may be ashamed to say we are uncertain of to 20s. For whether it be 9m 15s or 9m 40s is difficult to determine: I mean of Paris and Greenwich.

I beg you will answer for me the questions proposed to me by our worthy friend Dr. Morton on the part of Mr. Dunn. I observed the exit of Venus at Paris with a telescope of 18 feet, and an eye glass of 24 inches focus, and with a smoaked glass which was sufficiently dark, but I was not uncertain so much as a single second. M. Messier observed with a Gregorian telescope of 24 feet, magnifying very nearly the same as mine, and he agrees very well with me. M. Maraldi had a refracting telescope of 15 feet, but he was tired at the time; and M. de la Caille had a refracting telescope of M. Dollond's, which was not well put together, and did not terminate objects distinctly. I took for the moment of the contact the 1st instant of Venus's limb raising the sun's limb in the slightest manner. The account of these observations will be in the memoirs of the academy for 1761, which is almost printed off.

We reckon the longitude between Greenwich and Paris to be 9m 203: but I do not know what are the observations upon which it is founded. The preceding observations will contribute hereto.

C. The Observations of the Internal Contact of Venus with the Sun's Limb, in the late Transit, made in different Places of Europe, compared with the Time of the same Contact observed at the Cape of Good Hope, and the Parallax of the Sun from thence determined. By James Short,* A.M., F.R.S. p. 611.

In the summer of the year 1760, the R. s. resolved to send some fit persons to proper places of the globe, in order to observe the transit of Venus, which was to

Mr. James Short, an eminent optician and constructor of telescopes, was the son of a joiner at Edinburgh, where he was born in 1710, and died at Newington Butts, near London, in 1768, consequently at 58 years of age. When 10 years old, his parents being both dead, he was placed in Heriot's charity hospital at Edinburgh. Having manifested however uncommon talents for mechanics, &c. 2 years after, he was sent to the high school of that city, where he so much distinguished himself in classical learning, that his friends thought of qualifying him for a learned profession. After 4 years spent at the high school, in 1726 he entered as a student in the university of Edinburgh, where he passed through a regular course of study; took his degree of master of arts; 4 O


happen on the 6th of June, 1761. In consequence of this resolution, they appointed Messrs. Maskelyne and Waddington to go to the island of St. Helena, and Messrs. Mason and Dixon to go to Bencoolen, a settlement belonging to the East India Company on the island of Sumatra. Two reflecting telescopes of 2 feet focal length each, with an object glass micrometer of 40 feet focus adapted to one of them, an astronomical clock, and an equal altitude instrument, were ordered by the Society for each of those places. The munificence of his late and present majesty, patrons of the R. s. defrayed the expence.

Mr. Maskelyne and his assistant arrived at St. Helena in the month of April 1761; but Mr. Mason and his assistant, being detained at Plymouth by an accident, on their arrival at the Cape of Good Hope in the month of April 1761, found it was too late to reach Bencoolen, and therefore resolved to stay at the and at the earnest intreaties of his relations, attended the divinity hall, and in 1731 passed his trials to fit him for a preacher in the church of Scotland. Soon after this however the mind of our young artist began to revolt against the idea of a profession so little suited to his talents; and having had occasion to attend a course of Mr. Maclaurin's mathematical class in the college, he there so much distinguished himself, that the professor took great notice of him, and invited him often to his house, where he had an opportunity of knowing more fully the extent of his capacity. In 1732, Mr. M. kindly permited Mr. S. to make use of his rooms in the college for his apparatus, where he began to work in his new profession of telescope making, under the eye of his eminent master and patron; who, in a letter about 2 years after to Dr. Jurin, mentions the proficiency made by Mr. Short in constructing reflecting telescopes in these words: "Mr. Short, who had begun with making glass specula, is now employing himself to improve the metallic. By taking care of the figure, he is enabled to give them larger apertures than others have done; and, upon the whole, they surpass in perfection all that I have seen of other workmen." The figure which Mr. S. gave to his great specula was parabolical: which he did however not by any rule or canon, but by practice and mechanical devices. Mr. S. continued from this time to practise his art as a regular profession, with great success; so that when, in the year 1736, he was called up to London, at the desire of queen Caroline, to give instructions in mathematics to William, Duke of Cumberland, he had cleared the sum of 5001. by the profits of his business. Towards the end of the same year he returned again to Edinburgh; and having made several useful improvements in his art during his stay in England, he now prosecuted it with fresh vigour and success. In 1739, being then again at London, the Earl of Morton took Mr. ́S. with him on a tour to the Orkney isles, and engaged him there to adjust the geography of that part of Scotland. He returned to London with the Earl, and finally established himself there in the line of his profession. In 1743 he was employed by Lord Thomas Spencer, to make a reflector of 12 feet focus, the largest that he ever constructed, except those for the king of Spain, and some others of the same focal distance, with great improvements and higher magnifiers. The telescope for the king of Spain was finished in the year 1752, which, with its whole apparatus, cost 12001. But the instrument made for Lord Thomas Spencer, having fewer accompaniments, was purchased for 600guineas. From the great profits and success of his trade, Mr. S. left at his death a fortune of 20,0001.

Mr. S. was a good general scholar, and well skilled in optics and mathematical learning. He was a very useful member of the R. s. and wrote a number of excellent papers in the Philos. Trans. And his determination of the sun's parallax at about 83", from his ingenious calculations on the transit of Venus, in the above Memoir, has been pretty generally adopted by astronomers.

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