Mr. Porrett on a New Vegeto-Alkali in Gun-Cotton. 409 



is formed in the subterranean reservoir^ to the extent of pro- 

 ducing a sudden detonation. 



Be this as it may, as we desired to know whether the 

 natural eruptions of the Strokkur were produced more regu- 

 larly than those of the Geysir, and had any connexion with 

 them, we only forced the eruptions twice at our arrival, and 

 we noted, in the following table, all the great natural erup- 

 tions : — 



Dates. 



Forced 



Eruptions. 



Heights. 



Natural 



Eruptions. 



Hours. 



5th Julv, at S*" 57"" p.m. .. 

 9th July, at 4'' 15" p.m. .. 

 9th Julv, at Qh 25" p.m. .. 

 10th July, at 12" 15°' a.m. 

 12th July, at 8'' 2™ a.m. ... 

 13th July, at S"" 30" p.m..., 



30"'-210 



49'"-375 

 43'"-528 



not measured. 



not measured. 

 47'"-426 



It will be seen from this table that the natural eruptions of 

 the Strokkur do not present more regularity than those of the 

 Geysir, and that their coincidence with the latter, if it some- 

 times happens, is not general. 



Some observers have admitted that there was a direct com- 

 munication between the Strokkur and the Geysir: unfortu- 

 nately I was not able, during my visit, to collect water from 

 the Strokkur sufficiently freed from the earthy matters coming 

 from the clods of earth which we threw upon it during the 

 first days of our arrival, to bring it back and submit it to an 

 accurate analysis ; but the quantity of sulphuretted hydrogen, 

 which I found to be F'^'T^S per litre, differs sufficiently from 

 that which the water of the Geysir contains, to allow us 

 to conceive that these two springs, subjected perhaps to the 

 same cause of subterranean heat, are not, as has been thought, 

 in immediate connexion. 



LXI. On the existence of a New Vegeto-Alkali in Gun- 

 Cotton. By Robeut Pokrett, Esq.* 



\ T the last meeting of this Society on the 7th instant, a joint 

 ''*• communication from Mr. Teschemacher and myself "On 

 the Chemical Composition of Gun-Cotton" was readf, and 

 in the last paragraph but one thereof I suggested that a view 



• Communicated by the Clicniical Society; having been read Dec. 21, 

 1846. 



t This communication will be found at p. 273 of the present volume of 

 this Journal. 



