ADDITIONS AND CORnECTIONS. 



Xt 



ensile the cempositors to read ofF the references as correctly 

 fifom this method of notation as if they were written out at 

 length. If the number of coloars be found too great, the 

 difficulty may be easily removed by using only five, and 

 supplying the deficiency either by providing two instruments 

 •f different constructions, or by drawing the lines in a 

 greater variety of positions. 



P. 106. Col. 2, at the end, insert. 



The work ofacoalhea\'er on the river Thames 

 is considered as very laborious, but the effect 

 produced is not comparatively great. Four 

 men are employed in filling baskets in the hold 

 of the lighters.andjfour in " whipping"or elevat- 

 ing them from 1 2 to 20 feet, which is performed 

 by ascending three or four steps, and standing 

 on a stage, which descends while the baskets are 

 raised ; and the labour of filling and raising 

 them is nearly equal. The usual work of a day 

 is to raise 42 chaldrons, weighing about 126 000 

 pounds, that is, 31 500 pounds for each labour- 

 er, to the height of 16 feet, making 504 000 

 pounds, raised 1 foot, instead of 3 600 000, or .14 



But it is not difficult to do twice or twice and a 

 halfasmuch, andioschaldronareoften raised,or .3J 



There have even been instances in which 

 IBS chaldron have been raised, or .65 



P. 167. Col. 1. L. 4 from the bottom, for " Cazand" read 

 Cazaud. 



P. igs. Col. 1. L. 2, for " barculus" read barulcus. ' 



P. 25S.Col. l.L. 12, for "aerostation," read aerostatation. 



P. 278. Col. 2. L. ]?, for " v", read U. 



P. 319. Col. 1. L. 11 from the bottom, for " 170 " and 

 " l»0", read, ^Land J5. 



Col. 2. L, 7, after " case" insert as. 



L. 22, for " specimen" read spectrum. 

 L. 24, after " in," insert a. 



P. 330. Col. 1. L. 3. from the bottom, for " 3553", read 

 .3553. 



P. 354. Col. 1. 1. 20. for " '^' read nearly J. 



P. 356. Col. 2. After 1. 3 from the bottom, insert, 

 Olseroalions on the Sun's Light, 

 Heliostate. S'Gravesande's Natural Philosophy. 



P. 382. Col. 2, last Line, for " 56707° . . SneUius," read, 

 ,S6070 to 50802 Klostermann. 

 Si° 18' S. 57037 Lacaille, 1752. 



( 



56740 

 or 57070 Fernelius 

 55021 SneUius. 



) 



P. 364. Col. 1. L. 9 from the bottom, for "or" read the 

 diameters. 



P. 367. Col. 1. L. 29. for / read 1". 

 P. 367. Col. 2. L. 18, for "73j," read 39, or perhaps 48. 

 P. 337. C0I.2. L. 11. from the bottom, for " areometry" 

 read aerometry. 



P. 452. Col. 2, after 1. 2, insert. 



According to Kirwan's theorem, the mean temperature 

 of the year, and that of the month of April, is 84° — 26. 5 

 T. s. 2 I. The greatest mean heat of the summer months 

 may be found very nearly, according to Kirwan's table, by 

 this formula, 86— isv.s. 2Z — i.7v.s.i2 (/+15°), and 

 the mean heat of the month of January, which is the 

 coldest month by 80^29. 5 v. s. 22 — v. s. ' * I — ^v. s. 18 

 (1+7°). The error seldom amounts to more than adegree. 

 P. 455. Col. 1, after 1.20, insert, 



Laplace Exp. du syst. du monde, 267. Asserts that 

 " the attraction of the sun and moon does not produce, ei. 

 ther in the sea, or in the atmospfiere, any constant motion 

 from east to west." 



P. 455. Col. 2. after 1. 7 from the bottom, insert. 

 Remarks on the Effects of the Sun's Heat on the Atmo- 

 sphere. 

 It is very difficult to demonstrate conclusively that the 

 sun's relative motion from east to west has or has not such a 

 tendency as Halley attributed to it, to cause an easterly wind 

 in the neighbourhood of the equator ; it appears however 

 to be possible to show that no effect of this kind can be pro- 

 duced in any sensible degree. 



The immediate effect of the expansion of the air at any 

 place must be to cause a partial elevation of the surface of 

 the atmosphere : for the instant that this elevation remains, 

 the lateral pressure will be unequal at every part of the 

 height of the column except the basis, and the inequality 

 must become greater in ascending, being always proportional 

 to the difference cf the weights of the columns contiguous 

 en each side to any given point. The elevation may there- 

 fore be considered as the beginning of a wave, which will 

 be propagated each way with a certain velocity; and this 

 velocity must at first be less than that of a similar wave in a 

 fluid perfectly homogeneous, but will approach to it as it 

 spreads, the inequality of temperature soon disappearing. 

 If the cause of expansion continues, new waves will con- 

 tinually succeed each other, so that the surface will remain 

 horizontal. Hence will arise a pressure ; forcing the lower 

 parts of the air towards the point of expansion, and a cur- 

 rent will be produced, which will cause a continual circula- 

 tion. But it is obvious that no parts of the atmosphere can 



