158 Intelligence and Miscellaneous Articles. 
which may he easily overlooked.’ Now what confidence can be 
placed in all this as experimental research ? Van Marum found his 
batteries produce a heating effect proportional to the coated surface. 
Cuthbertson, by his most exceptionable method of breathing into his 
jars when he wanted a greater effect, did, it is true, obtain a higher 
ratio, yet no direct satisfactory comparison between the quantity 
discharged and the heat produced was ever arrived at, and various 
results ensued. This we see admitted at page 182 of Mr. Cuth- 
bertson’s work, Exp. 149; here the law in question evidently failed : 
at page 185 we observe that when the quantities of electricity were 
said to be as 2: 3, another result ensued; for experiments 150 and 
151 show that the lengths uf wire fused, instead of being as 4: 9, 
were as 2:6, that is, as 1:3. It is quite impossible to repose 
any confidence in such a state of things. Indeed, we have only 
to examine Mr. Cuthbertson’s experiments attentively as given in 
his work, and in Nicholson’s Journal, 4to, vol. ii. p. 218, to be 
assured of the inexactitude of the experimental processes. In the 
latter we find the lengths of wire melted to be as the quantity of 
electricity: see p. 218. However true, therefore, it may be that 
Cuthbertson obtained results which led him to imagine that twice the 
quantity of electricity would melt four times the length of wire, he 
cannot be said to have demonstrated and established that law; and 
I may therefore, without any philosophical injustice, claim to have 
been the first to have clearly developed that law by exact electrical 
measurements, and by new methods of research, as my paper dated 
1825, and quoted in the Journal of the Royal Institution, 1830-31, 
fully shows. There also will be found the hypothesis advanced by 
Mr. Joule, that increased velocity is probably the source of the qua- 
druple heat. I endeavour to show that the heat is as the velocity with 
which the unit of charge traverses the wire, that a double quantity 
passes with a double velocity, and the effect is ‘‘ as the momentum,” 
or quantity into velocity. I again therefore ask Mr.’Thomson to state 
when or where I ever announced “‘as an experimental result,” that the 
heating effect of an electrical discharge was ‘‘ simply proportional to 
the quantity of electricity.” Mr. Joule, in referring to my paper in 
the ‘Transactions’ for 1834, appears to have confounded this question 
with that of the same quantity accumulated under different electro- 
meter intensities, a question discussed in my late differences with 
Dr. Riess. What I said in my paper in the ‘ Philosophical T'ransac- 
tions,’ and which I still insist on, was simply this: viz. that under 
whatever electrometer intensity you accumulate a given quantity of 
electricity, provided the battery surface be undivided, that quantity, 
when discharged through a metal wire, will still excite in it the 
same degree of heat. Thus if a quantity of electricity = A, for 
example, be collected on a Leyden jar, exposing 2°5 square feet of 
coating, and then be collected on a jar exposing 5 square feet of 
coating, I say, that notwithstanding the electrical intensity in these 
two cases may be as 4:1 nearly, yet that the discharge of the 
quantity A in each case will excite the same heat in a metallic 
wire; that is, if the same charging rod and circuit be employed. 
And I ask the gentlemen to whom | have just alluded, to make that 
