364 THE POPULAR SCIENCE MONTHLY. 



two pieces of gold are placed one in a cell of nitric and the other in 

 one of hydrochloric acid, separated by an earthen-ware partition, no 

 chemical action takes place ; but, if the two pieces be connected by a 

 wire, the acids immediately attack them. In 1840 he was elected a 

 Fellow of the Royal Society, and in 1841 he published a paper "On 

 the Combinations, by the Voltaic Battery, of Azote and Hydrogen 

 with Metals." This same year he excited a great deal of interest by 

 exhibiting, before the Electrical Society, daguerreotype pictures en- 

 graved by electricity. The picture was joined witli the positive pole 

 of a battery, and placed in hydrochloric acid ; the chlorine set free at- 

 tacked the silver surface unprotected by mercury, and from this etched 

 surface an electrotype was made to be printed from. Though now in 

 active practice at the bar, he continued his electrical investigations. 

 He brought out his voltaic gas-battery, and wrote a paper on its ap- 

 plications to endiometry ; published a " Memoir on the Action of 

 Phosphorus, Sulphur, and the Hydrocarbons in the Gas-Pile ; " and a 

 communication on the " Electric Action by the Apjjroximation of 

 Dissimilar Metals without Contact," in which he showed that when 

 a disk of zinc and one of copper are approximated w^ithout touching, 

 and then separated, the gold leaves of an electroscope diverge, prov- 

 ing the existence of a radiating force capable of exciting electrical 

 disturbance. In January, 1842, Mr. Grove delivered a lecture at the 

 London Institution " On the Progress of Physical Science," in which 

 the doctrine of the correlation of physical forces was briefly but clear- 

 ly enunciated. He delivered a course of lectures at the same place, in 

 which he explained and illustrated the propositions briefly laid down 

 the year before. The position he sought to establish was that heat, 

 light, electricity, magnetism, chemical affinity, and motion, are all 

 correlatives; that is, that either of them, as a force, may produce the 

 others. As an illustration, in one of these lectures he used a train of 

 revolving wheels ; the smallest, or that which revolved most rapidly, 

 was of metal, and contained a piece of phosphorus in it. While this 

 revolved with great raj^idity, the phosphorus remained cool, but by a 

 contrivance the wheel was suddenly stopped, and the phosphorus took 

 fire ; the object of the experiment being to show that arrested motion 

 becomes heat. In 1847 he issued his work " On the Correlation of 

 Physical Forces;" and in 1852 he published a memoir in the "Philo- 

 sophical Transactions," on the " Electro-Chemical Polarity of the 

 Gases." In 1856 he experimented upon the application of electricity 

 as a mechanical power, and showed that, when by electrical attraction 

 or repulsion, a weight is suspended, it is at the expense of electric 

 tension, and that the spark cannot traverse the same distance that it 

 could traverse, with the same apparatus and charge, without the eleva- 

 tion of the weight. Other researches of his have been on " The Elec- 

 tricity of Flame" and the formation of a flame-pile capable of produ- 

 cing chemical decomposition. 



