VOL. LII.] PHILOSOPHICAL TKANSACTIONS. 647 



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. 



XCVIIL 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, 17 62. p. 586. 



For this purpose Mr. M. had a post about 10 feet long erected in a conveni- 

 ent 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 ob- 

 servations may sei^ve 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, 5^ 16'" p.m. he took the 

 following observations of the altitude of the water by the side of the post 11, 12; 

 9±, 13^; 10, I24-; 9, I44-; 9, 12-1; 9-L, 13^; 10, 13; 9, 14; 9, 13; 9, 14. 

 The medium of all is 1 1-^ for the true altitude of the water. Mr. Mason at the 

 same time by about as many observations found 1 1-5^. 



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, 11^ 15™ a.m. by a mean of 69 observations taken in this 

 manner, he found the altitude of the water to be 3-jVjj.; and at 1 1'^ 21™ a.m. by 



