On the Maximum Magnetic Effect of Electromagnets. 253 



whereas a salt of the formula C12 H^ Ng 2HC1 PtCl4, would 

 contain 33'05 per cent. It is evident that the oil consists of 

 two substances ; and I am at present engaged in effecting 

 their separation, as one of these only volatizes with water- 

 vapour. I hope ere long to be able to communicate the 

 results of some experiments with this curious body. 



Physiological Action. — In conjunction with Professor 

 McKendrick, the physiological action of several substances 

 described in this Journal for October 1876, and in this paper, 

 have been ascertained. The results will form the subject of. 

 a more extended memoir ; I shall give here, however, a short 

 sketch of their action. Pyridine, picoline, lutidine, and 

 their salts have a very slight action, apparently producing 

 drowsiness. The methyl iodides of these bases are intense 

 irritants to the cerebral centres, and produce paralysis of the 

 fore limbs. The action is of the same kind, but even more 

 intense, with ethyl and allyl derivatives. Dipyridine and 

 dipicoline produce the same eifect, but even more strongly ; 

 and when combined with methyl or ethyl iodide they are 

 fearful poisons. 



The ammonium salt of dicarbopyridenic acid proved to be a 

 tremendous excitant, producing fits resembling epilepsy; 

 curiously, its methyl ether had no appreciable effect. The 

 general law appears to be that the more complicated the body 

 the more energetic its action; but the effect also depends 

 largely on the specific character of each substance. 



XXXIII. On the Diameter of the Wire to he employed in ivind- 

 ing an Electromagnet in order to produce the Maximum Mag- 

 netic Eff'ect. By R. S. Beough *. 



IN 1866 Mr. Schwendler investigated the best galvanometer 

 resistance to employ in testing with Wheatstone's bridge, 

 a question which was previously involved in complete obscu- 

 rity, some physicists arguing that, since near balance the cur- 

 rent passing through the galvanometer approaches the indefi- 

 nitely small, therefore the number of convolutions, and hence 

 the resistance of the galvanometer ought to be indefinitely 

 great \. 



I may here remark that Count du Moncel, in a communica- 

 tion to the Academy of Sciences, has unjustly criticised 

 Mr. Schwendler's method of treating the subject of electro- 



* Eead before the Asiatic Society of Bengal on the Gth of April, 1877, 

 and communicated by the Author, 

 t Philosophical Magazine, May 1866, 



