1B26.] Mr. Christie on the Magnetism of Iron, S^c, 2? 



decided evidence, it is more delicate than any, even than the 

 method by the fluid tests. For the proof of what is now stated 

 I must refer your readers to my paper just published. I may 

 merely mention, that in two judicial cases to which I have lately 

 applied it, I was able to detect a twentieth part of a grain in the 

 contents and coats of the stomach ; and that I am satisfied I 

 could detect half that quantity. 



In your criticism you have done me the injustice of condemn- 

 ing my process with obscure hints, and without even mentioning 

 what the process is. I must, therefore, add a single sentence, 

 that your readers may know what we are contending about, and 

 be encouraged to look at what I have said elsewhere on the 

 subject. My plan now consists in presenting the same portion 

 of the poison successively in the state of the sulphuret, the metal, 

 and the oxide : — the sulphuret in the state of an impure, some- 

 times shining precipitate ; the metal in that of a brilliant crystal- 

 line crust ; the oxide in that of adamantine, octahedral crystals s 

 and the fluid tests are discarded altogether. The characters I 

 mention may be all seen distinctly with a fortieth part of a grain ; 

 and I have even sometimes succeeded with a hundredth part 



only. 



1 hope I may request you will insert the foregoing observations 

 in the Amiah ; and I have the honour to remain, 



Your obedient servant. 



To R. Phillips, Esq, S^c. R. Christison. 



*:j^"* In a future number of the Annals, I shall probably offer 

 a few observations on the foregoing communication. — R. P. 



Article VII. 



Abstracts of Papers in the Philosophical Transactions for 1825, 

 on the peculiar Magnetic Effect induced hi Iron, and on the 

 Magnetism manifested in other Metals, ^c, during the Act of 

 Rotation. By Messrs. Barlow, Christie, Babbage, and 

 Herschel. 



{Continued from vol. xi. p. 449.) 



2. On the Magnetism of Iron arising from its Rotation, 

 By S. H. Christie, Esq. MA. FRS. (With a Plate.) 



For some time previously to his observation and investigation 

 of the phaenomena detailed in this communication, Mr. Christie 

 had been engaged in making several series of experiments, with 

 a view to discover the precise manner in which unmagnetized 

 iron acts upon a magnetic needle. For this purpose, he had 

 made use of an iron ball 13 inches in diameter, and also of a 



