2. 



68 REPORT — 1860. 



The author further extended it by supposing that the amount of the power of effect- 

 ing surface condensation is dependent upon, and corresponds with, the actual weight 

 of the atom, but that the repulsive force which keeps the atoms asunder, acting 

 in a contrary direction to the cohesive force, prevents that cohesive force from per- 

 ceptibly acting upon the molecules of the medium in which the atom is placed. 



Resuming the consideration of the atomic constitution of compounds, particular 

 attention was directed to the fact that, in a series of compounds of one metal (oxide 

 for instance), it would be found that the compound possessing the most neutrality (the 

 least activity) would have the greatest atomic number. The term " atomic number " 

 was defined as " denoting the total number of elementary atoms capable of being 

 contained within the space which would be filled by a single atom, of hydrogen." 

 The numbers brought forward by the author were quoted from Gmelin's works ; but, 

 as Gmelin's atomic numbers denoted the number of compound atoms capable of being 

 contained within a given space, his (Gmelin's) numbers were by the author multi- 

 plied by the total number of elementary atoms contained in an atom or equivalent of 

 the compound. Thus, taking equal bulks of lead and oxide of lead, it will be found 

 that if the lead contains 1218 atoms, the oxide of lead will contain 1888 atoms, half 

 of them oxygen, and the other half lead atoms. The following, amongst other series, 

 were brought forward : — 



Atomic number. 



( Chromium 2333 Active. 



J. < Sesquioxide of chromium. . S610 Neutral. 



( Chromic acid 2500 Active. 



Manganese 3220 Intermediate. 



Protoxide of manganese . . 2948 Most active. 



Peroxide of manganese. ... 3777 Neutral. 



( Manganic acid ? 



Iron 3203 Most active. 



„ Magnetic oxide 3486 Intermediate. 



I Sesquioxide 3715 Most neutral. 



Ferric acid ? 



J Lead 1218 Most active. 



Oxide ditto 1888 "1 Tt ,. . 



Pb'O* 1953/ Intermediate. 



Peroxide of lead 2475 Most neutral. 



I Mercury Perchloride 878 Most active. 

 Ditto Protochloride 975 Intermediate. 

 Mercury 1485 Least active. 



Thus in the first series quoted the compound endowed with the most inactivity, the 

 most neutrality, possesses also, of the three, the greatest atomic number, so that in the 

 union of two atoms of chromium with three atoms of oxygen in the production of this 

 compound, viz. the sesquioxide, considerable condensation must occur. Chromium 

 is chemically active in one direction, oxygen in another; and on bringing the two 

 together, the opposing forces appear to neutralize, and balance each other ; if the pro- 

 portion of oxygen is increased, if one atom of chromium is united with three of oxygen, 

 a compound is produced, not neutral, but endowed with great activity ; and connected 

 with that activity is the important fact, that its constituent atoms are wider apart 

 than the constituent atoms of the sesquioxide, the neutral member of the series. 

 Examining the succeeding scries in a similar manner, equally striking and interesting 

 results were obtained. 



The paper concluded with the following remarks : — 



To seek for an explanation of the phenomena we have been studying is a natural 

 impulse; that an explanation cannot be given without resorting to hypothesis is very 

 obvious ; but if an hypothesis can be advanced which will connect the facts together, 

 which will tend to enlarge our views upon the subject, and which will not be incom- 

 patible with well-known and established facts, surely that hypothesis, whatever it 

 may be, is worthy of our present attention. There is no need to imagine the existence 

 of any new force, any new agency ; the whole of the phenomena can be satisfactorily 



