4 
MR. J. J. WATERSTON ON THE PHYSICS OF MEDIA COMPOSED OF 
In a few important respects Waterston stopped short. There is no indication, 
so far as I can see, that he recognised any other form of motion, or energy, than the 
translatory motion, though this is sometimes spoken of as vibratory. In this matter 
the priority in a wider view r rests with Clausius. According to Waterston the 
ratio of specific heats should be (as for mercury vapour) 1*67 in all cases. Again, 
although he was well aware that the molecular velocity cannot be constant, there 
is no anticipation of the law of distribution of velocities established by Maxwell. 
A large part of the paper deals with chemistry, and shows that his views upon 
that subject also were much in advance of those generally held at the time. 
The following extract from a letter by Professor McLeod will put the reader into 
possession of the main facts of the case:— 
“ It seems a misfortune that the paper was not printed when it was written, for it 
shadows forth many of the ideas of modern chemistry which have been adopted since 
1845, and it might have been the means of hastening their reception by chemists. 
“ The author compares the masses of equal volumes of gaseous and volatile elements 
and compounds, and taking the mass of a unit volume of hydrogen as unity, he 
regards the masses of the same volume of other volatile bodies as representing their 
molecular weight, and in the case of the elements he employs their symbols to indicate 
the molecules. 
“ In water he considers that the molecule of hydrogen is combined with half a 
molecule of oxygen, forming one of steam, and he therefore represents the com¬ 
pound as HOi. He does not make use of the term “ atom ” (although he speaks of 
atomic weight on p. 18, but thinks it divisible), and if he had called the smallest 
proportion of an element which enters into combination an atom, he would probably 
have been led to believe that the molecules of some of the simple bodies contain two 
atoms, and he might have adopted two volumes to represent the molecule, as is done 
at the present time. The author calls one volume or molecule of chlorine Cl, one 
volume or molecule of hydrogen H, and one volume or molecule of hydrochloric acid 
HiCh. If he had regarded the molecules as containing two indivisible atoms, these 
bodies would have been represented, as now, by the formulae Cl 2 , H 3 , and HC1 
respectively, all occupying two volumes. § 15 showos bow near he was to this 
conception. Gerhardt in the Fourth Part of his ‘ Traite de Chimie Organique,’ 
published in 1856, points out the uniformity introduced into chemical theory by the 
adoption of this system. 
“For carbon he makes C = 12, as now accepted, although I do not find how he 
arrives at this number. He seems to have anticipated one of Ramsay’s recent 
discoveries, that nitrous anhydride (hyponitrous acid, ON,, No. 26 in the table) 
dissociates on evaporation into nitric oxide (binoxide of nitrogen, No. 28) and nitric 
peroxide (nitrous acid, No. 25). 
“ The values for the symbols for sulphur, phosphorus, and arsenic taken from the 
vapour densities (and which are multiples of what are believed to be the true atomic 
weights), cause some complexity in the formulas of their compounds. 
