1 



Mr. Mullins on the Voltaic Battery. 37 



transition of vast masses of air through the temperature of the 

 dew-point, can only occur in serene weather at sunset and not 

 at sunrise. The inflamed appearance of the morning sky, 

 considered indicative of foul weather, is, I have no doubt, 

 owing to such an excess of humidity being present, that clouds 

 are actually being formed by condensation in the upper re- 

 gions, contrary to the direct tendency of the rising sun to dis- 

 sipate them, which must therefore be considered as indicating 

 a speedy precipitation of rain. 

 Edinburgh, 4th February, 1839. 



VII. Observations on an improved Construction of the Voltaic 

 sustaining Battery, By F. W. Mullins, Esq., F.G.S. 

 F.S.S., Si-c.'' 



"^HREE years have elapsed since I introduced to the 

 public at one of the Friday-Evening Meetings at the 

 Royal Institution, my mode of construction of the voltaic 

 sustaining battery. This battery was then in its simplest 

 form, being nothing more than a coil or cylinder of copper 

 inclosed in a thin bladder containing a solution of sulphate 

 of copper, both being placed in an earthenware pot, holding 

 a cylinder of amalgamated zinc immersed in a solution of 

 muriate of ammoniaf. In this arrangement the sulphate of 

 copper solution had communication with the internal as well 

 as the external surface of the copper cylinder; but subsequent 

 experiments having convinced me that there was no use, but 

 rather an injurj', in permitting access of the sulphate solution 

 to the internal surface of the copper, I altered the arrange- 

 ment so far as to close the bottom of the cylinder, and throw 

 the whole of the salt of copper, as it dissolved, upon a shelf at 

 the upper part of the cylinder, through holes in its circum- 

 ference on a level with the shelf z'wifo the space hetvoeen the two 

 metallic surfaces, where of course it was most needed. The first 

 of these arrangements was worked for a short time after it was 

 made public at the Adelaide Gallery of Science, the other sub- 

 sequently, and both are described in the Phil. Mag. for Oct. 

 1836. I am thus particular in adverting to the two modes of 

 construction adopted by myself, in consequence of ascertaining 

 that some would-be scientific persons, with less of discretion 

 or honesty than of puerile vanity, have since the period re- 

 ferred to attempted to arrogate to themselves whatever merit 

 there might have been in the arrangement in which the sul- 

 phate solution is used internally as well as externally ; and 

 I have reason to know that batteries so arranged have been 

 palmed upon many as superior to those which after a long 

 * Communicated by the Author. 

 I See Phil. Magazine for October 1836, p. 283. 



