1878. J 
Liquefaction of Oxygen. 
237 
me on the ground of an enlarged conception of space, should 
be denied, only one other kind of explanation would remain, 
arising from a moral mode of consideration that at present, 
it is true, is quite customary. This explanation would con- 
sist in the presumption that I myself and the honourable 
men and citizens of Leipzig, in whose presence several of 
these cords were sealed, were either common impostors or 
were not in possession of our sound senses sufficient to per- 
ceive if Mr. Slade himself, before the cords were sealed, 
had tied them in knots. The discussion, however, of such 
a hypothesis would no longer belong to the dominion of 
science, but would fall under the category of social decency. 
Some other still more surprising experiments — prepared by 
me with a view to further testing this theory of space — have 
succeeded, though Mr. Slade thought their success impos- 
sible. The sympathising and intelligent reader will be able 
to understand my delight caused thereby. Mr. Slade pro- 
duced on me and on my friends the impression of his being 
a gentleman : the sentence for imposture pronounced against 
him in London necessarily excited our moral sympathy, for 
the physical fadls observed by us in so astonishing a variety, 
in his presence, negatived on every reasonable ground the 
supposition that he in one solitary case had taken refuge 
in wilful imposture. Mr. Slade, in our eyes, therefore, 
was innocently condemned — a vidfim of his accuser’s and 
his judge’s limited knowledge. 
VII. LIQUEFACTION OF OXYGEN.* 
By M. Raoul Pictet. 
CjPjHE objedt which I have had in view for more than 
'LL three years is to demonstrate experimentally that mo- 
lecular cohesion is a general property of bodies, to 
which there is no exception. 
If the permanent gases are not capable of liquefying, we 
must conclude that their constituent particles do not attradl 
each other, and thus do not conform to this law. 
Thus, to cause experimentally the molecules of a gas to 
* The liquefaction of oxygen is so important a scientific achievement that 
we have much pleasure in laying before our readers the following detailed 
account of the means employed and diagrams of the apparatus used, which 
were communicated to us by M. Pidtet himself. — Ed. Q. J. S . 
