Catalogue Raisonné. 473 
The relative equivalents might be thus arranged :— 
At. weight. Theory. Experiment. 


Manganese, - - 28 42.4 45.5 
Arsenic, = = - 38 57.6 51.8 
a3 Loss, 2.7 
Mang. + Ars. “ 66 100.0 100.0 
_ Ona New Salt obtained by the partial decomposition of Per- 
chloride of Mercury. By R. Puinuips, F.R.S.L. & E.—Phil. 
Mag. (New Series.) No. XXXVIII. 
Gay Lussac had already, in his stenographed lectures, mentioned the forma- 
tion of sub-chloride of mercury, by mixing the per-chloride with the per- 
oxide, and some other processes. By putting hard carbonate of lime, 
such as Iceland spar, into a solution of corrosive sublimate, months are 
required to obtain even a few crystals of the salt. The dipermuriate 
may, however, be obtained, free of all admixture, by dissolving 1 atom, 
= 272 grains, of per-chloride of mercury in water, heating the solution, 
and adding to it 648 grains, =3 atoms, of per-oxide of mercury, obtain- 
ed either by decomposing the per-nitrate with heat, or corrosive subli- 
mate with potash. ‘The author gives a further analysis of the salt, by 
which it would appear that it consists of 

One atom of muriatic acid, = - 3f7 or 7.8 
Two atoms of per-oxide of mercury, > 432 or 92.2 
469 100.0 
An Introductory Treatise on the Nature and Properties ef Light, 
and on Optical Instruments. By W. M. Hieeins. Nimmo, London. 
Blackwood, Edinburgh. 1829. 
This little work is composed of many pretty historical recollections, and 
much physico-mathematical speculation. The pervading spirit of the 
book is the shadow of a conjunction between the stern truths of mathe- 
matics, for which Mr. Higzins professes a high reference, and the tanta- 
.  lizing deceptiousness of what is called physical science, to wit, such sub- 
jects as “ the ultimate divisibility of matter,” ‘‘ the naiwre of light,” 
“the causes of reflection and refraction,” &c. 
Mr. Higgins has perhaps here wandered into a darkness in the mysteries 
of physics, which the light of mathematics will serve but faintly to illu- 
minate, and has probably been a little deceived in supposing that he can 
demonstrate the infinite divisibility of matter by geometrical figures. 
The author does not lay claim to much originality, his object being “ to 
assist those who, like himself, are climbing the hill cf science ;” but 
states that his “‘ opinions concerning the nature of light are in some 
degree novel.” These opinions appear to be comprised in the proposi- 
tion, that “‘ when the spheres of attraction which surround any parti- 
cles of matter are destroyed, those particles produce light,”—a view in 
which, from certain facts observed in the production of caloric, we are 
much inclined to coincide. 
We cannot give more than one specimen of the author’s reasoning.—Hav- 
ing remarked that the supposition of the penetrability of matter depends 
upon the doctrine of the mfinite minuteness of the particles, he contends 
that it is easily proved that ‘ matter is divisible ad injinitum,”’ and rests 
his proof upon the supposition, that the tangent of a circular are A, 
could not be brought in contact, in every point, with an arc of another 
circle B, described from a centre at an indefinite distance in the line of 
the radius of the circle A; or, in other words, he presumes the tangent 
line to be absolutely straight, and therefore incompatible with any arc of 
acircle. x uno, &c. 
Elementary remarks on optical instruments conclnde the work, which, on 
the whole, we have found to be a very pleasant book to read. 
VOL, I, 30 
