1865.] Physical Science. 733 



then broke out again in the early morning of August 3rd. This 

 lasted till midnight, and the disturbance then ceased altogether for 

 twenty-four hours, renewing itself on the following day. Mr. Stewart 

 exhibited drawings, showing the nature of the magnetic disturbance, 

 and then compared it with the greater outbreak of August, 1859. 

 Both consisted of two separate outbreaks, and both began during the 

 hours of night or early morning. One peculiarity accompanying 

 both storms was that there was at the time many spots in the surface 

 of the sun. Many of them rapidly altered their size and their cha- 

 racter, and one of these phenomena consisted of a bright spot of light 

 rapidly crossing a dark spot on the surface of the sun. In conclusion, 

 he said that it would be hasty, at this stage of our knowledge, to jump 

 to any conclusion on the subject. 



The physical papers this day concluded with an interesting 

 notice by Dr. J. H. Gladstone, "On the Eefraction Equivalent of 

 Carbon ; " the remainder of the papers being strictly mathematical. 



On Saturday the 9th September, the proceedings opened by 

 Professor J. D. Forbes reading a paper on " The Laws of the Con- 

 duction of Heat in Iron Bars," being a resume of observations made 

 with the aid of a grant from the Association. The subject had 

 occupied his attention for the last fourteen or fifteen years, and was 

 a very old problem. He had reported in 1852 on the progress he 

 had then made in his experiments, and he now came forward to explain 

 what he had done since in that respect. He had, without reference 

 to either the precise mathematical or physical laws on .which such 

 estimates had been based by different philosophers, sought to deter- 

 mine the loss of heat from a given bar by direct experiments, and 

 without necessarily inquiring what the precise law is. At the same 

 time his experiments could not be quite regarded as conclusive, and 

 he would be very glad if some member of the Association would 

 extend them. 



Mr. J. P. Gassiot, V.P.E.S., next read a paper, " On the Change 

 of Form and Colour which the Stratified Discharge assumes when 

 a varied Eesistance is introduced in the Circuit of an extended Series 

 of the Voltaic Battery." Mr. Gassiot operated with a battery com- 

 posed of 4,000 insulated glass cells, and instead of sulphate of 

 copper, as used by the late Professor Daniell, he put about a table- 

 spoonful of sulphate of mercury into each cell. The elements, 

 carbon and amalgamated zinc, were then introduced into the cells, 

 which were subsequently filled with rain-water. When one of the 

 wires of the battery is inserted in the water, and the other wire 

 touches the moistened surface of the glass, but is not in actual 

 contact with the water, a luminous discharge is produced, entirely 

 filling a tube which is prepared to receive it, without any appearance 

 of stratifications. On depressing the wire, discs of red light are 

 rapidly produced from the positive pole, and on further depression 

 nineteen only of these discs remain in the tube, and these are much 

 increased in brilliancy and distinctness. On still further depression, 

 other singular and highly beautiful effects are produced. Mr. Gassiot 



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