176 Remarks on the Essay of Dr. Berzelius (MAttei', 



perhaps ; those of oxygen may be regular tetrahedrons j those of 

 azote may be cylinders of equal diameter and altitude; &c. &c. 

 But if we understand atom in the latter sense, then not only the 

 elementary atoms, but most of the compound atoms, are probably 

 spherical, spheroidical, or some fig^ire approaching to that of a 

 sphere. Of all compound atoms, that consisting of 3 elementary 

 atoms is probably most remote from a sphere; but when ttxe com- 

 pound one contains 5 or more simple ones, the figure must, I 

 should suppose, be virtually a sphere. 



What Dr B. says of the electric polarity of atoms (vol. ii. p. 447) 

 makes no necessary part of the atomic tlieory such as I maintaii). 

 Neither does the conclusion that 2 atoms of A cannot combine with 

 2 of B, 2 of A with 3 of B, &c. Such combinations, I appre- 

 hend, rarely exist ; but 1 see no reason, either from theory or 

 experience, for rejecting them. It may be said that such compound 

 atoms are capable of division : true. Byt the parts may instantly 

 unite again by virtue of an affinity ; and hence they cannot, 

 peritajK, be exhibited in a divided state. Olefiant gas, for instance, 

 is known to consist of carbon and hydrogen united in tlie ratio of I 

 atom to 1 : but there is nothing that I know of to prevent their 

 uniting 2 atoms of carbon to 2 of hydrogen, and the 4 atoms to be 

 placed in the form of a rhombus, those of hydrogen being at the 

 extremities of the longest diameter. Nitrous acid, too, may be 

 Adduced as an instance of 2 atoms of azote and 3 of oxygen. And 

 •even nitric acid seems most frequently to he found in composition 

 »s if constituted of 2 atoms of azote and 4 of oxygen united to 1 

 of base. However unlikely this may be, I see no absurdity in 

 supposing that if 2 atoms of nitric acid, such as I haye delineated 

 in my Chemistry, were contiguous, they might coalesce by affinity, 

 aiwi refuse to take a third atom or compound of the like kind. 

 Hence 1 disclaim tlie axiom that every compound atom must have 

 a single atom for its nucleus or centre. 



So much for the differences in our conceptions of the principles 

 of the atomic theory. We come next to the difficulties to which 

 J)x. Berzelius apprel^ends it is liable. 



" The first of these difficulties is the circumstance that there are 

 combustible bodies, iron, for example, which unite only with two 

 doses of oxygen, the second of which is only ]i times greater than 

 the first" Here I perfectly agree with Dr. Berzelius, both as to 

 the existence of the difficulty, and as to the solution of it which h*> 

 has given. When the oxygen in the (supposed) protoxide of any 

 metal is to that in the deutoxide as I to 1-i-, that is, as 2 to 5, it is 

 to be presumed that the real first oxide is not known, and that those 

 two which are known are the second and third oxides. But this is 

 not the only solutim which such cases admit of, as will appear 

 presently. My ideas on the oxides of iron w<re settled from some 

 experiments 1 made in 1807, compared with the experiments of 

 others then published. I concluded that 100 iron combine with 28 

 •oxygen by solution in sulphuric acid, forming what is called tine 



