by Dr. Van Marum. 32 1 



21. Continuation of the experiments cm the oxy dating of 

 metals', on this occajion, the femi-vietah. — As the femi- me- 

 tals could not be drawn out into fine wire, thin plates of them 

 were employed ; but this could be the cafe only with zinc 

 and bifmuth. After the explofion the metal was feen to rife 

 up like a thick vapour, leaving traces of it on the paper; but 

 it could not be converted into ignited globules. Purified an- 

 timony, pulverifed and ftrewed in a line, was oxydated, and 

 exhibited the fame phenomena as zinc and bifmuth ; but a 

 larger quantity was converted into powder before it could be 

 oxydated Some femi-metals were mixed with fo much tin 

 that they could be drawn out into wire T ' of an inch in dia- 

 meter; for example, ', zinc and j tin, ' cobalt and ~ tin, 

 •j' T bifmuth and || tin. In their oxydation, however, they 

 exhibited nothing particular; they always rofe in vapour, and 

 left fpots on the paper like the unmixed metals. A platina 

 wire, jj inch in diameter, made by Jeanetv at Paris, exhibited 

 the fame phasnomena in fufing as filver. The platina was 

 ftrewed about in fine powder, which left. on the paper traces 

 almoft fimilar to thofe of iron. 



22. The fo-called refiduum after the explofion was, with a 

 charge of 5 , double of what it was by a charge of 15 . 



23. Nairne found that, with a battery of 50 fquare feet of 

 coating, the jars were readily broken, when the charge waa 

 made to explode by too fljort. a difcharging-rod, and he con- 

 fidcred one of five feet in length fufficient to prevent this ac- 

 cident. Dr. Van Marum found this length fufficient for 

 135 feet of coating, but not for 225 feet; and, for 550 feet, 

 a difcharging-rod of 18 feet in length was not fufficient, for 

 even then the jars were fometimes broken. None of the 

 jars however were hurt when the communication was not 

 made through the ftrong iron wire of the battery, but through 

 very line metallic wires, through imperfect conductors, ani- 

 mals, and the like, where the ft ream found more refiftance. 

 In charging la r ge batteries it is neceltary that the difcharg- 

 ing-rod fhotild receive the ft ream from the middle of the lot- 

 tery, for, when it was received on one fide, two jars broke in 

 fuccelfion on the oppofitp fide with a charge of 20°, Brool .-; 



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