AS OBSEEVED IN TOEEICELLIAN AND OTHEE VACUA. 
157 
sides of the vacuum-tubes ; and Pluckee has shov^n that it arranges itself between the 
poles of a powerful electro-magnet in the line of magnetic force. In this communica- 
tion I have shown not only the appearance of the dhection of a force as evinced when 
passing through a narrow orifice, but that wherever this discharge impinges heat is 
evolved. At present I do not alter the opinion that I ventured to offer, that the dark 
band may be due to interference ; but the new facts which have been elicited in relation 
to the negative discharge requffe a further, and probably an extended experimental 
investigation, and I am at present engaged in endeavouring to test the accuracy of the 
opinion I have offered, by means of apparatus now in the progress of construction. 
107. I am aware that in this paper I have entered somewhat more fully into detail, 
when describing my experiments, than is usual in communications to the Royal Society, 
but I have been induced to be thus minute, as the subject is novel; and by explain- 
ing some of my experiments in detail, it may afford to others the means of examining 
directly, and possibly more correctly, into the nature of that mysterious force which we 
denominate Electricity, and which is in many respects so nearly related to heat, mag- 
netism, and other forces, each being, as Mr. Geove has long since shown, convertible 
into each other ; while the fact that a vacuum so perfect can be obtained in a closed 
vessel containing such a substance as hydrate of potassa, would excite a hope that the 
limi t to vaporation, the existence of which Faeadat* and others have, if not proved, at 
least rendered so probable, may be determined, and even its consequences exhibited by 
dhect experiment. 
John P. Gassiot. 
Clapham Common, 
December 8, 1858. 
l^ote. — Received January 11, 1859. 
Since I sent my communication to the Royal Society, I have again obtained a non- 
conducting vacuum mthout the introduction of sulphur or selenium (95). In the 
extremity of a tube. No. 140, 40 inches long, inch internal diameter, four pieces of 
caustic potash were inserted ; the tube was then charged with carbonic acid, exhausted 
and hermetically sealed, as akeady described ; in this state the potash was carefully 
heated by a sphit-lamp until it melted ; the tube being slowly turned, the potash on 
gradually cooling covered the surface of that portion of the tube in which it had been 
placed ; in this manner it presented a large surface ; in a short time the remainder of the 
carbonic acid was absorbed, and the vacuum thus formed no longer conducted the 
discharge. 
If two vacuum-tubes which conduct are attached, one to the inner and the other 
to the outer terminal of an induction coil, without being otherwise connected with 
each other, a reciprocating discharge will take place in each, that from the outer 
being far more vivid : if the circuit is now completed, either by a wire or by a tube 
* Philosophical Transactions, 1826, Part III. p. 484. 
