Bibliography. 385 
equivalents, which different substances contain under the same bulk or 
volume; these have been called the atomic numbers, and we find the 
atomic numbers of the elements are often connected by simple ratios, 
and that substances of the same natural group have usually the same 
number of equivalents contained under the same volume.” 
The combining volumes of substances have evidently an important 
relation to the atomic numbers, as also the atomic volumes, obtained by 
dividing the equivalent weights by the specific gravities, and which may 
be considered as expressing the relative volumes of their atoms. 
Another and very interesting point, is that of resemblance in crystal- 
line form, for we find asa general rule, that those bodies closely resem- 
bling each other in chemical properties have the same crystalline form. 
Late researches have tended to confirm the law announced by Dulong 
and Petit, that the specific heats of equivalent weights of bodies are 
equal, or are connected by simple multiples. 
But to come to the classification itself. The elementary bodies are 
divided into fourteen classes, of which we can say little more than to 
mention their names. 
The first group embraces eight members. Oxygen, sulphur, selenium, 
tellurium, chlorine, bromine, iodine and fluorine. These are connected 
by their strong affinities for the substances of the other groups, by the 
fact that any one of them may replace another, wholly or in part, in 
any compound without altering its molecular type, and without altering 
in kind its chemical relations. Very close relations are also observed 
between their equivalents and atomic volumes, and several of them are 
connected by isomorphism. ‘They are also the most highly electro-neg- 
ative of all substances. 
The second group consists of nitrogen, phosphorus, arsenic and an- 
timony. 
The third of hydrogen, zinc, cadmium, and magnesium ; the salts of 
the three last are well known to be isomorphous, and Dr. Kane has point- 
ed out a close resemblance between the compounds of zinc and hydro- 
gen, so that it is not improbable that if hydrogen could be sufficiently 
condensed it would appear as a metal. 
The fourth is composed of iron, manganese, chromium, cobalt, and 
nickel ; the natural resemblances are pointed out in a clear and forcible 
manner, but our limits will not permit us to give any thing more than the 
groups and the substances composing them. 
The fifth consists of aluminum, glucinum, and zirconium. 
The sixth of molybdenum, tungsten, vanadium and columbium. 
The seventh group comprises copper, mercury, bismuth and palladium. 
The eighth is composed of barium, strontium, calcium, lead and silver. 
The ninth group consists of platinum, titanium, iridium and osmium. 
The tenth embraces gold, uranium, rhodium and tin. 
