Charging of 'Jars. — St/lplate of Strontian In Gtouce/lerfhire. 53 J 



the edge of the coating. With regard to the wire, the only place from which it explodes 

 fpontaneoufly, is that part which is nearly of an equal height with die edge of the mouth of the 

 jar. The fluid is nearly as much condenfed on this part as on the other, fo that an explofion 

 from the wire is hindered by the fame caufe as from the coating. A jar under fuch cir- 

 cumftanccs cannot, therefore, explode fpontaneoufly ; but the fluid will run over the edge of 

 the jar as quickly as the machine furniihes it, when its charging capacity is full. 



I have ftated, at page 530, that a jar of the dimenfions there given, being clean and dry, 

 can only contain a charge fufllcient to fufe 2 inches of a certain wire, and when breathed 

 into, its charging capacity will be fo much encreafed, that it will contain a charge fuflicient 

 to fufe 8 inches of the fame fort of wire ; and a battery of i j jars, in the firft-mentioned 

 ftate, can only fufe 20 inches, and in the laft-mentioned, 60 inches. This increafed charg- 

 ing capacity, proceeds, no doubt, from the particles of moifture, though not from their afting 

 as a coating, as has been fuppofed, but by their being brought into a ftate or capacity of re- 

 (ifting a fpontaneous explofion, fo that a ftronger charge is forced in upon the coated part. 

 Some of the eleftric fluid which was forced upon the uncoated part to a certain height 

 (perhaps ^ an inch, more or lefs, according to the degree of dampnefs, and the fituation of 

 the particles) may, indeed, be difcharged along with that from the coated part j but this 

 is of little importance, and by no means capable of producing that increafed eficft, which, 

 as I have fhewn by experiment, would require an addition of feven jars to a battery of 

 fifteen. 



II. 



Dtfcovery of Sulphate of Strontian^ near Sodbtiry, in Glouceflcrfnre. By G. S. GiBBZS, 



B. M. F. R. S. 

 To Mr. NICHOLSON. 



I 



SIR, 



F the following imperfeft analyfis fliould meet your approbation, I fhall feel myfelf flat- 

 tered by feeing it noticed in your excellent monthly publication. 



I have the honour to be, 



Sir, 

 Bath, Your humble fenant, 



No. 28, Gay-ftreet. GEORGE SMITH GIBBES. 



A friend of mine, the Rev. Mr. Richardfon, fome little time fince, (hewed me a fpecimcn 

 of a fubftance which, he fiid, was found in great abundance in the neighbourhood of Sod- 

 tury, in Gloucefterfhire, where it was ufed for the purpofe of making gravel walks. The 

 ftone was compofed of a vaft number or fmall cryftals, which cohered together with but 

 little force. The cryftals were eafily reduced to powder, and were not afll'fted by any acid. 

 i expofed equal parts of thcfe cryftals in the ftate of a fine powder and charcoal to the 



3 Z 2 adioii 



