Analytical Essay on Asparagus. 33 
The author of a paper in the Supplement to the Ency. 
Brit. vol. ii. p. 641, informs us that, ‘ according as we look 
at an object more or less juminous, these variations (of the 
pupil) are so great, that in the observable variations of the 
human eye the aperture is thirty times as large at one time 
as at another.” 
Whence it may be easily understood, that a cottage, seen 
through a thick fog, may form as large a picture in the eye 
as a castle when strongly illuminated by the sun’s rays. 
I am, sir, 
Your humble servant, 
Ez. WALKER. 
VII. Analytical Essay on Asparagus. By M. Rostaver 
junior, Apothecary at Vale de Grace*. 
Some time ago M. Parmentier engaged the apothecaries of 
the Military Hospital to repeat the experiments of M. An- 
toine on asparagus, for the sake of giving us a subject of 
study fit to exercise us. My colleagues gave it specially i in 
charge to me to follow this labour ; auf I undertook the task 
with pleasure, conceiving, at first, that it would be an easy 
one. But as my first essays created some doubts in my 
mind respecting the truth of the facts which had been an- 
nounced, and as there are besides many vegetable substances 
of which the distinguishing properties are but little known, 
I was necessarily involved in very considerable embarrass- 
ment. I strove, however, with redoubled efforts against 
these obstacles, till I collected the facts which I have the 
honour to present to you. 
As in every analysis we should endeavour to isolate, as 
conveniently as possible, each of the substances which com- 
pose a whole; in place of following the process pointed out 
by M. Antoine, which prescribes making a strong decoc~- 
tion of asparagus, then to evaporate it to obtain the extract, 
&c., I thought it preferable to employ at first a mechanical 
analysis, that I might not be exposed to change certain sub- 
* From Annales de Chimie, tom. lv. p. 152. 
Vol. 26. No. 101. Oct.1806. C stances 
