26 REPORT—1862. 
tric current, well depend entirely upon the amount of resistance offered by the magnetic 
element as an outlet to the electric force. If the iron is hard, and the resistance con- 
sequently great, the amount of work will be but small; but if the iron is soft and 
the resistance offered small, then the amount of force transformed into magnetism 
and available for mechanical purposes will be greater. 
In a paper read before the Chemical Society in March last, the author showed 
that the same principle holds true also in regard to heat. When heat is applied 
to a solid or a liquid body, a portion of the heat goes to raise its temperature, and 
another portion is consumed in internal molecular work against cohesion. The 
rising of the temperature and the separation of the molecules are the two paths 
or outlets for the force, and the relative proportion which passes through each is 
determined here in like manner by the resistance offered by each to the passage of 
the force. Hence the reason why the specific heat of bodies increases as their 
temperature rises; for the resistance offered by cohesion decreases with rise of tem- 
erature, thus allowing a greater proportion of the heat applied to become latent in 
mternal molecular work. It was stated as a general principle that, other thinys being 
equal, the more easily fused a body is the greater is its specific heat. This was shown 
also experimentally to be the case. 
In conclusion, in the production of molecular work by heat or mechanical work 
by means of electro-magnetism, there exists no fixed relation between the amount 
of heat applied and the work performed, for in both cases the quantity of work 
varies with the molecular resistance offered. 
On Electric Cables, with reference to Observations on the Malta-Alewandria 
Telegraph. By Dr. Ernest Esse.Bacu. 
The three sections of this cable touching the shore at Tripoli and Benghazi 
represent three condensers of 75,000 to 150,000 feet square, which, on account of their 
size, disclosed several important facts in regard to the nature of the dielectric, 
They allowed, in the first instance, a clear separation of the residual charge from the 
resistance test. Dr. Esselbach arrived thereby not only at the true resistance of 
gutta percha, but attained a new and entirely different test for insulation (electri- 
fication test), by which the absence of electrolytic action in the covering could be 
distinctly ascertained. These observations further afforded proof that the residual 
charge on Leyden jars was not a penetration of electricity like that of heat in a 
metal, but an increase of the specific inductive capacity of the material, and merely 
a function of time, analogous to certain corresponding phenomena of torsion and 
magnetism. The absolute quantity of charge, as ascertained in Dr. Esselbach’s pre- 
vious paper, showed that an increase in inductive capacity of one per cent., under 
the influence of electric tension, was sufficient to account for what appeared to the 
galvanometer as a change in resistance amounting sometimes to as much as 50 per 
cent. 
Dr. Esselbach further showed his diagrams on earth-currents, extending over 
one month’s observation, indicating the great advantage which two lines of 500 
and 600 miles from east to west, and one from north to south, in one continuation, 
sh and the facility and precision with which they are observed by Wheatstone’s 
ridge. 
The cable is taken roughly as being 2000 times better than the old Atlantic cable ; 
and whereas in this latter at least 80 per cent. of the strength of current was lost in 
the transit, more than 99 per cent. actually arrives in the present case at the other 
end. The speed of a signal through this cable has been ascertained in different 
ways, and in the most perfect way by Captain Spratt, C.B., incidentally, upon a 
comparison between the longitude of Malta and Alexandria. The time for one 
signal through the whole length of 1300 miles approaches one second nearly. The 
author drew attention to the fact that the question of practical speed, after having 
first been brought into prominence by Mr. Latimer Clark’s experiments, had re- 
mained in abeyance since Professor Thomson’s researches at the time of the laying 
of the Atlantic cable, after which all interest had been absorbed by the insulation 
question, and very rightly, since it was first necessary to establish communication, 
and with certainty, before trying to precipitate it. This appearing now assured by 
