42 REPORT — 1853. 



dine, made by treating arrow-root with nitric acid of specific gravity 1-5. After re- 

 maining about six years unaltered, this specimen suddenly began to give off gases, 

 and in a few weeks' time nothing remained of the original xyloidine, but in its place 

 a light brown viscid liquid. 



After describing the various chemical substances of which this decomposed mass 

 consisted, the author proceeds, " We may suppose that the decomposition of this 

 sample of starch xyloidine has taken place in somewhat of the following manner : — 

 some of the peroxide of nitrogen has split up into nitric oxide and nitric acid, whilst 

 a small portion of the nitrogen has combined, as might be expected, with some of the 

 hydrogen of the compound to form ammonia, and a larger quantity has combined 

 with carbon and hydrogen to form prussic acid. During this process oxygen must 

 have escaped as such, or combining with carbon have passed off as carbonic acid, or 

 it may have been consumed in the formation of the slightly acid principle which has 

 been described as found in considerable quantity among the resulting solids. 



" Whether the ammonia and the nitrous fumes have reacted upon one another 

 ■with the formation of nitrogen gas and water, I know not. 



" The separation of so much carbon in the form of cyanogen must be looked upon as 

 the principal cause of so much water being produced, for the viscid mass is essentially 

 a strong aqueous solution of the organized bodies. A very large portion of the starch, 

 freed from its combined nitric acid, has remained in a gummy condition, perhaps as 

 dextrine, though it was certainly not of the variety colourable by iodine ; whilst the 

 change had advanced further with another portion, and it was converted into sugar. 

 These substances, with traces of a bitter principle, and of a singular odoriferous sub- 

 stance, were the only products of decomposition, at least as far as I could detect." 



On the Conduction of Electricity hv Flame and Gases. 

 By W. R. Grove, M.A., Ph.D., F.R.S. 



A somewhat extended series of researches has been recently carried out by 

 M. Edmond Becquerel with a view to determine the conducting power of flame and 

 of hot ail'. These investigations have led M. E. Becquerel to conceive that he has 

 proved the conducting power of both for electricity. The apparatus employed was a 

 platinum tube, with the conducting wire passing through it. Mr. Grove has adopted 

 a somewhat different arrangement. This consisted of a glass tube, with two copper 

 wires inserted through corks at either end ; from these within the tube proceeded a 

 piece of platinum wire, which, by connexion with the battery, could be brought to a 

 state of intense ignition. In this state these were adjusted at the distance of -^'jjth 

 of an inch apart, and then connected with the powerful voltaic combination of 

 Mr. Gassiot. Notwithstanding the proximity of the wires, no trace of electricity 

 could be detected as passing through the interposed stratum of heated air. Mr. Grove 

 inclined to the opinion, that the effect described by M. Becquerel was more analogous 

 to the disruptive discharge than to conduction, as it was stated not to take place until 

 the solid bodies arrived at red heat, and then to be increased by attenuating the gases, 

 though at temperatures below that point ; no degree of rarefaction allowed any elec- 

 tricity to be transmitted. 



On the Origin and Composition of the Mineral called JRoitensfotie. 

 By Professor Johnston, M.A., F.R.S. L. .^ E. 



Note on the Formation of Magnesian Limestone. 

 By Professor Johnston, M.A., F.R.S. L.^ E. 



The author produced specimens of magnesian limestone formed by deposition from 

 a spring near the village of Neesham upon the northern banks of the Tees. This 

 limestone possessed the colour, general appearance and porous structure of the lime- 

 stones of the county of Durham, and contained as much magnesia as some of the 

 purer beds of magnesian limestone in tliat county. From the production of this 

 limestone he reasoned as to the deposition of dolomitic limestones in general, and the 

 relative probability of the two theories which ascribe their magnesia to the impreg- 

 nation of previously existing limestones, either by sublimation from beneath, or by 

 percolation from above. He considered both agencies inadmissible as general causes, 

 and was favoiu'able to the view that as a general rule magnesian limestones were de- 



