VOL. LXXVIII.^ PHILOSOPHICAL TRANSACTIONS. 40g 



more clear from the observations I shall now make on the manner in which the 

 discharge is produced. When the astonishing velocity, with which the charge 

 of a jar or battery moves through a considerable space, is considered, it may at 

 first appear impossible, that the discharge should be made by the alternate giving 

 and receiving such small quantities as those by which the charge was produced ; 

 yet a more ample consideration of the matter will, I think, show that it cannot 

 possibly be brought about any other way. I presume it will be granted, that the 

 charge of a jar, in discharging, either leaves it all at once, or goes out by the 

 same small quantities by which it went in. To suppose any intermediate manner 

 would neither lessen the difficulty, nor would it be consonant to any of the 

 known laws of electricity. 



If then the whole charge leave the jar all at once, there must be a point of 

 time at which the jar will be without any electric fluid either on one side or the 

 other : nay more, suppose a large jar or battery to be discharged by means of a 

 few inches of thin wire, there will then be a point of time at which the 

 whole quantity of electric fluid, which constituted the charge, must be contained 

 in a piece of wire, weighing only a few grains. Now, if it be considered, that 

 time, like matter, is infinitely divisible, may we not rather suppose, that the 

 discharge of a jar is nothing more than an inconceivably rapid succession of such 

 small quantities as may be sent off, without causing such a destruction of the 

 equilibrium as the laws of electricity seem not to admit ? That this supposition 

 is not quite free from objections I readily admit ; but before they are permitted 

 to overthrow it, let it be well considered, whether they are, on the whole, as 

 strong as those I have stated against the opposite opinion, which I think may be 

 pronounced to militate not only against what has been here mentioned as a fun- 

 damental law of electricity, but also against every known fact, 



X. Experiments on the Cooling of Water below its Freezing Point. By Charles 

 Blagden, M. D., Sec. R. S., and F. A. S. p. 125. 



When the experiments for determining the degree of cold at which quicksilver 

 becomes solid, related in the Philos. Trans, for 1783, were under consideration, 

 no difficulty occurred in explaining the phenomena that had been observed, ex- 

 cept in the few instances where the mercury in the thermometer congealed, 

 while it was surrounded with some of the same metal in a fluid state. The 

 well-known property of water, that under different circumstances it will bear to 

 be cooled several degrees below its freezing point without congealing, afforded 

 from analogy the most probable solution of this difficulty ; but as neither the 

 cause of that property had been investigated, nor the circumstances by which it 

 is modified had been ascertained, I was led to attempt some experiments on the 

 subject ; not only in hopes of elucidating the above-mentioned phenomenon of 



VOL. XVI. 3 G 



