.-,oo 



ELECTRICITY. 



DcripuT <J8 4. tin- thermometer at 1; of Reaumur, and Saus- 

 hygrometer at 65. 



I .: 



meub by 



1 .- --; 



1-. i \:. 1 ..,:: 



Experi- 

 ment* of 

 Cuthbert- 



Experi- 

 ment! of 

 Singer. 



The effect of lightning in Aiding metals is so familiar 

 to every reader, that it is scarcely necessary to mention 

 it. Money is often melted in the pockets of those struck 

 with lightning ; swords have been melted in their scab- 

 bards ; and the le.iden frames of church windows have 

 been frequently fused. There is in the possession of 

 Thomas Allan, Esq. of Edinburgh, a curious parcel of 

 nails, which were struck with lightning on the road 

 between Oxford and London. They have a very sin- 

 gular appearance, and are obviously expanded into 

 twice their original diameter. 



The power of electricity to oxidatemetals, was observed 

 by Beccaria and other electricians ; but it is to Mr Cuth- 

 bertson that we are indebted for the most complete series 

 of experiments upon this subject. The apparatus which 



he employed i* represented in Plate CCXI.VI. Fig. 7. 

 and co;i>ibU of a cylinder of glass alt, 8 inches high. ;iml 

 in ili.imrur. On the lower brass cap b is sere w- 

 cd a stop-cock, and in the inside of the vessel is fixed n 

 Mii.-ill roller, on which a quantity of wire, attached to a 

 packthread at intervals of 4 inches, is coiled. A bra-* 

 tuln- a, about 3 inches long, is screwed into the centre 

 of the upper cap />, and, by means of a long needle, the 

 t ml of the packthread and wire is thrust through it, and 

 hog's lard is placed in the t nix.-, so that the wire and pack- 

 thread may move through it air-tight. In this way the 

 wire i* extended in the centre of the glass cylinder, and 

 when one length of it is exploded, another may be drawn 

 forward by means of the contiguous packthread with- 

 out opening the cylinder. In order to ascertain the 

 quantity of air absorbed during the process, a gage, 

 shewn separately at A, about 10 inelu s long, and made 

 of a glass tube, is screwed into the lower end of the 

 stop-cock, and immersed in a vessel of quicksilver, the 

 rise of which, when the stop-cock is opened, will be a 

 measure of the air absorbed. 



The air left in the receiver after a numl>er of explo- 

 sions, is always found to have been deprived of a por- 

 tion of its oxygen ; and if hydrogen or nitrogen be sub- 

 stituted in place of atmospheric air, the metal will not 

 suffer any oxidation, but will be melted, and minutely 

 divided. 



The following Table contains the results of Mr Cuth- 

 bertson's experiments : 



DMcr: 



Experi- 

 ments of 

 Ciulibert 

 COD. 



In these experiments, Mr Cuthbertson employed very 

 high charges, which is attended with great risk to the 

 jars. Mr Singer repeated the experiments with shorter 



and finer wires, and with a moderate charge, and ob- Experi. 

 taincd the following results : menu of 



Singer. 





Mr Singer's experiments were not performed in re- 

 ceivers. The wires were stretched parallel to the sur- 

 face of a sheet of paper, at the distance from it of |th of 

 an inch. When the explosion is made over glass, a 

 part of the metal, in an unoxidated state, appears imme- 



diately under the wire, while the part of it which is Figure cf 

 oxidated produces around the other a figure of some the oxide*. 

 width. In this case the figures are more beautiful, but 

 less permanent than when they are impressed on paper. 

 These experiment* are generally made with high 



