480 Royal Society : — 



the bromide one about 20, and the one from the iodide liquid about 

 22*2. The quantities deposited by a single equivalent of zinc were 

 about 42'5 in the chloride, 50 in the bromide, and 51 in the iodide 

 solution. 



The explanation proposed of their formation is, that the antimony 

 in depositing, being in the " nascent " state, combines chemically in 

 a feeble manner with the saline ingredients of the electrolyte ; but 

 the complete sources of the evolved heat remain undecided. 



"On the Sulphur-Compounds in Purified Coal-Gas, and on Cry- 

 stallized Hydrosulphocarbonate of Lime." By the Rev. W. R. 

 Bowditch, B.A., F.C.S., Wakefield. 



"On the Geometrical Isomorphism of Crystals." By the Rev. 

 W. Mitchell. 



"On the Forces concerned in producing the larger Magnetic 

 Disturbances." By Balfour Stewart, M.A., F.R.S. 



The author begins by alluding to a previous communication made 

 to the Royal Society, containing an account of the great magnetic 

 storm of August 28-September 7, 1859, in which he had shown 

 that the first effect of this great disturbance was to diminish in 

 intensity both components of the earth's magnetic force at Kew, 

 during a period of about six hours. Such an effect, he argues, can 

 scarcely be supposed due to any combination of earth-currents, of 

 which the period is only a few minutes. 



But another appearance is noticeable on the photographic curves 

 which regard the progress of this great disturbance. 



While the great wave of force had a period of about six hours, 

 there were superimposed upon it smaller disturbances having a 

 period of a few minutes, and therefore comparable in this respect 

 with earth-currents. 



These smaller disturbances are of very frequent occurrence, and 

 show themselves in the Kew magnetograph curves as serrated appear- 

 ances, occasionally magnified into peaks and hollows. 



Two hypotheses may be entertained regarding them. 



1st. They may be conceived to represent small and rapid changes 

 in the intensity of the whole disturbing force which acts upon the 

 magnet ; and since (as stated above) this force cannot be supposed 

 due to earth- currents, so neither can its variations be caused by these. 



2nd. The peaks and hollows may be supposed due to the direct 

 action of earth-currents upon the magnets. 



The following argument is advanced to show that the second of 

 these hypotheses is untenable. 



Let us compare together the two magnetic disturbances of August 

 and September 1859 and August 1860; and suppose the peaks 

 and hollows of the disturbance curves of these dates to be caused by 

 earth-currents. This would require that currents of the same name 

 should have simultaneously travelled between Margate and Ramsgate, 

 and between Ramsgate and Ashford during the latter disturbance, 

 whereas during the former these currents should have been of 

 different names, that is to say, the one positive and the other negative. 



