On Nodes and Loops in connexion with Chemical Formula. 367 



through the centre is an advantage, is that of the deflecting 

 magnets for determining the intensity of the earth's magne- 

 tism, which may be thus made lighter without much dimi- 

 nishing their magnetic moment. 



In conclusion, let me express my regret at the imperfection of 

 the theory given in this paper ; for although the equations are 

 more general than any yet given, yet still they rest upon two 

 quite incorrect hypotheses ; and so, although we have found 

 these formulae of great use in pursuing our studies on magnetic 

 distribution, yet much remains to be done. A nearer approxi- 

 mation to the true distribution could readily be obtained ; but 

 the result would, without doubt, be very complicated, and would 

 not repay us for the trouble. 



In this paper, as well as in all others which I have published 

 on the subject of magnetism, my object has not only been to 

 bring forth new results, but also to illustrate Faraday's method 

 of hues of magnetic force, and to show how readily calculations 

 can be made on this system. For this reason many points have 

 been developed at greater length than would otherwise be 

 desirable. 



XLII. On Nodes and Loops in connexion with Chemical Formula. 

 By Oliver J. Lodge, Demonstrator of Physics in University 

 College, London*. 



(1) A T the recent Meeting of the British Association, Professor 

 xl Cayley communicated to Section B his investigation 

 "On the Analytical Forms called Trees/' the principal chemical 

 result of which was the determination of the number of isomeric 

 paraffins for any given number of carbon atoms. He did not deal 

 with any case where the carbon atoms form a closed chain or 



C— C 



cycle as \ / or CcC, but only treated of simple ramifica- 



tions such as C-C 



x c-c 



In the discussion after the paper, Professor Clifford said that 

 a paraffin (or hydrocarbon of the form C n H 2?i+2 ) could not pos- 

 sibly form a closed chain or cycle of atoms, but must be a simple 

 ramification, and, further, that in a hydrocarbon of the form 

 C n H 2 »+ 2 -2x there would always be x cycles — as, for instance, in 



* Communicated by the Author. 



