1878.] 



On the relative ; ' Facility of Production" 



51 



have still hesitated to mention this, as I have been hopino- for an in- 

 crease of optical power which would have enabled me to be quite 

 certain on the point. My aperture (6 inches Cooke) is not adequate 

 to put the result beyond all doubt. 



As, however, the question has been raised, it is better at once to 

 state the attempt and its result, and to ask others with greater optical 

 power to search for the lines ; taking the precaution to use the cylin- 

 drical lens close to the eye, and not to apply it to the instrument until 

 the rays to be examined are absolutely in focus on the slit, if a slit is 

 used. It is possible scintillation may help matters. 



V. " On the relative ' Facility of Production' of Chemical Com- 

 binations." By Sir B. C. Bkodie, Bart., D.C.L., F.R.S. 

 Received November 21, 1877. 



(Plate 4.) 



A circumstance which cannot fail to impress the student of 

 chemistry is the extreme paucity of chemical substances. The com- 

 binations of which he can conceive are innumerable, but those which 

 he can realize are few — a mere sprinkling from the sea- shore sand — 

 and, making the fullest allowance for human incapacity, it yet appears 

 that there are natural facilities and natural obstacles in the way of 

 making certain compounds which are independent of our skill and 

 power. 



It is my object to show that among these is to be reckoned that 

 relative "facility of production" of chemical substances which depends 

 on the mathematical laws of combination which are inherent in the very 

 nature of chemical combination and unalterable. By this I mean the 

 relative facility with which the units of matter may be constructed 

 and taken to pieces, owing to the relation of these units to the number 

 and kinds of the simple weights of which they are made up ; and I 

 propose to consider in what way, if any, this unequal " facility of 

 production " is connected with these mathematical laws. Is it true 

 that, as a matter of theory, there arises from these laws any greater 

 facility for the production of one compound than of another, or do all 

 stand on the same level ? and, further, does experience tally with the 

 conclusions of theory ? 



In my second Memoir,* on the Calculus of Chemical Operations, I 

 have shown that the unit of every chemical substance is to be re- 

 garded as constituted by the performance of the several operations 

 a, x, f • • • • upon the unit of space, and have also shown f 

 that the ultimate analysis of every chemical event leads to the con- 



* " Phil. Trans.," toI. clxvii, part i, p. 35, 1877. 



f Loc. cit.y p. 115. 



E 2 



