173 Dr. Tyndall on Diamagnetism and MagneoystaUic Action, 



one right and the other left, and addinj; a little water, and a 

 little patience, the crystal was at length reduced to a sj)hcrical 

 form. The ball was then washed, and its surface carefully 

 cleansed in dilute hydi-ochloric acid. The first pair of balls were 

 from the neighbourhood of Clitheroe in Jjancashire. 



Table V. — Spheres of Calcareous Spar, 9*2 millims. diameter. 



The spar from which these balls were taken was not quite 

 transparent; to ascertain whether its dullness was due to the 

 presence of iron, a ciystal which weighed about 3 grammes was 

 dissolved in hydrochloric acid; the solution was exposed in a 

 flat basin to the air, and the iron, if present, suffered to oxidize ; 

 fen'ocyanide of potassium was added, but not the slightest tinge 

 indicative of iron was perceptible. 



A series of experiments were next made with a pair of spheres 

 of calcareous spar from Andreasberg in the Harz Mountains. 



Table VI. — Spheres of Calcareous Spar, 10'8 millims. diameter. 



w=5. 



The spar from which these balls were taken was perfectly 

 transparent. After the experiment, the balls were partially dis- 

 solved in hydrochloric acid, and the solution tested for iron, as 

 in the former case — no trace of iron was present. 



The conclusion to be drawn from all these experiments, and 

 from many others which I forbear citing, is, that the law of 

 increase for a diamagnetic body is exactly the same as for a 

 magnetic — a rcsillt in*econcilable with that arrived at by M. 

 riucker. I had proceeded further with this investigation than 



