Conductors of Electricity, and during Electrolysis. 261 



3. It was absolutely essential to work with a galvanometer, 

 the indications of which could be depended upon, as marking 

 definite quantities of electricity. I bent a rod of copper into 



Fig. i. 



the shape of a rectangle (A B, fig. 1.), twelve inches long, and 

 six inches broad. This I secured in a vertical position by 

 means of the block of wood C ; N is the magnetic needle, 

 3f inches long, pointed at its extremities, and suspended upon 

 a fine steel pivot over a graduated card placed a little before 

 the centre of the instrument. 



4. On account of the large relative size of the rectangular 

 conductor of my galvanometer, the tangents of the deviations 

 of the needle are very nearly proportional to the quantities 

 of current electricity. The small correction which it is ne- 

 cessary to apply to the tangents, I obtained by means of the 

 rigorous experimental process which I have some time ago 

 described in the ' Annals of Electricity*'. 



5. I have expressed my quantities of electricity on the basis 

 of Faraday's great discovery of definite electrolysis, and I 

 venture to suggest, that that quantity of current electricity 

 which is able to electrolyze an atomic element expressed in 

 grains in one hour of time, be called a degree. Now by a 

 number of experiments I found that the needle of my galva- 

 nometer deviated 33°' 5 of the graduated card, when a cur- 

 rent was passing in sufficient quantity to decompose nine 

 grains of water per hour ; that deviation, therefore, indicates 

 one degree of current electricity on the scale that I propose to 

 be adopted. We shall see in the sequel some of the practical 

 advantages which I have had by using this measure. 



6. The thermometer which I used had its scale graduated 

 on the glass stem. The divisions were wide, and accurate. 

 In taking temperatures with it, I stir the liquid gently with 

 a feather ; and then, suspending the thermometer by the top 

 of its stem, so as to cause it to assume a vertical position, I 

 bring my eye to a level with the top of the mercury. In this 



* Vol. iv. pp. 131-132, and 476. 



