Chemistry and Physics. A13 
hen populine is boiled for a few minutes with baryta ck a color- 
less liquid is obtained, which, after the separation of the ex of ba- 
ryto by means of a current of carbonic acid, contains thing "bit sali- 
cine and benzoate of buryta. With bichromate of potash and sulpbu- 
ric acid populine yields hydruret of salicy!’ in nee Piet by boiling 
with stroug nitric acid it is transforined into nitro- benzoic, trinitro- 
phenic, and pa 8 acids; finally under the influence of acids it is re- 
solved into beuzvic acid, saliretine and grape sugar. When popu- 
line is Nog in ten or twelve times its weight of pure nitric acid 
1°30, a new substance is produced which the author calls benzo- 
helicine seit which bears the same relation to helicine which eta a 
ars to salicine. Benzo-helicine is transformed into helici 
benzoic acid when boiled with caustic magnesia.— Comptes Reitus: 
Xxxiv, | 
hem istry of Perfumery. —Hormann has communicated in a 
letier to Liebig some interesting facts in reference to the substances 
now used extensively i in flavoring syrups, sugar drops, &c. ssence 
of pine apple is a solution of butyric ether in alcohol; essence of jar- 
gonelle pear a solution of acetate of amyl; essence of apples a solu- 
tion of valerianate of amyl, Oil of cognac and oil of grape are also 
_ compounds ; artiticiat oil of bitter almonds: (essence of mirbane) 
@ more or less pure nitro-benzol. ee der Chemie und Pharmacie, 
Ixxxi, 87, Jan., 1852. W.G 
1. Nolte respecting pes tiimeasions and Refracting Fae of, the 
Eye; by Prof. J. D. Forses, (Proc. Roy. Suc. Edinb., Dec. 3, 4 
p- 251.) —Whilst cic asl on the sibject of Vision, i cnaated 
some recent authorities on the dimensions and curvatures of the re- 
fracting apparatus of the eye; and having calculated from them the 
Converyence of rays within the eye, it may save trouble to others to 
ut them on record. 
measures of he eye given in almost every English work on the 
subject, are those given by Young on his own aathority, or that of Petit. 
In the fifth volume of Dove’s Repertorium, I find a series of measures 
cobiisied by ‘T'reviranus from his own and preceding observations, which 
have converted below from French lines into decimals of an English 
inch. In these the’ teehee are hen pr spherical. In the same 
work of Dove, I find a series of measures by Dr. Krause of Hanover, 
on eight recent human eyes, pabiohn seem to have been made with un- 
Common care, and in which the deviation of the surfuces from sphericity 
is noticed. | -have preferred these last for the purpose of calculation, 
because ail the measures are taken from the same eye, which is not ihe 
. 
Treviranus. have consulted the 
than in the centre ; (2.) The anterior curve of the cornea y nearly 
oe the Mens oat ba ea® ; (3.) The anterior Sietacs 0 f the lens 
elliptical, the lesser diameter ey in the axis of vi lon, the ween 
oueianel is parabolic; (4) The figure of the retina, or the posterior 
surface of the v arenes bomen she stamp 
