1818.] Annular Eclipse of the Sun. 257 



Warm them a little by the fire (if the weather be cold) to prevent 

 their cracking when applied to the flame of the candle : then 

 draw one of them gently, according to its whole length, through 

 the flame ; and part of the smoke will adhere to the glass. 

 Repeat the same operation, only leaving a little part at one end 

 now untouched ; repeat the operation, leaving a further part at 

 the same end untouched, and so each time leave a further part of 

 the same end untouched, till at last you have tinged the glass 

 with several dyes, increasing gradually in blackness from one 

 end to the other. Smoke the other glass in like manner, and 

 apply the two glasses, one against the other, only separated by 

 a rectangular border, cut of brass or card paper, the smoked 

 faces being opposed to each other, and the deepest tinges of 

 both placed together at the same end. Tie the glasses firmly 

 together with waxen thread, and they are ready for use. The 

 tinge at one end should be the slightest possible, and at the 

 other end so dark that you cannot see the candle through it. By 

 this contrivance, applied between your eye and the sun, you will 

 have the advantage not only of seeing the sun's light white, 

 according to its natural colour, and his image more distinct than 

 through common dark glasses, but also of being able to inter- 

 cept more or less of his light as you please, and as the clearness 

 or thickness of the air requires it, by bringing a darker or lighter 

 part of this combined dark glass before your eye ; which will be 

 a great convenience at all times, but particularly when the bright- 

 ness of the sun is liable to sudden changes from flying clouds." 



I shall merely add, that it is to be hoped the Sovereigns of 

 the different provinces and states, mentioned in this Memoir 

 (page 184), will encourage persons from the neighbouring coun- 

 tries to enter and observe this eclipse : and that the love of 

 science will induce them to prevent such persons from beincr 

 subject to any tarif, or vexatious delay at the Custom-house, on 

 account of any astronomical or philosophical instruments whicli 

 they may take with them for the purposes of observation. 



Article V. 



Researches on various Fatty Bodies, and particularly on their 

 Combinations with Alkalies. By M. Chevreul. 



{Concluded from p. 199.) 



M. Chevreul's Sixth Memoir* 

 The subject of this memoir is the different kinds of fat; pau- 

 ticularly that of man, of the sheep, the ox, the jaguar, and the 

 goose. Before he enters upon the proper topic of this memoir, 



• Abstracted from Ann. de Chim. et dePhye. ii. 339. (A.ug. 1816) 



Vol. XII. N° IV. R 



