XVI. PRKSIDKXTIAL ADDRESS. 



to fraud. It is now about twenty years past, in 1H7H, when 

 scientitic interest was awakened by the experiments, then beinj,' 

 carried out by Cailletet of Paris and Pictet of (reneva, in 

 the liquefaction of the gaseous elements. Very little havinj^ 

 been done since the time of Faraday. Up to that date, although 

 a number of the more dense gases were liquefied by him, 

 some five or six resisted all atteiupts and ingenuity of the time, 

 and some of these were looked upon as being beyond the pos- 

 sibility of liquefaction, so were thought to be permanent gases, 

 until Pictet demonstrated the fact by liquefying oxygen and so 

 upsettingthetheory of permanency. He reasoned that if permanent 

 gases are not capable of liquefying, we must conclude that their 

 atoms do not attract each other, and this does not conform to 

 the law of cohesion. Since the time of these researches and ex- 

 periments, gas compression and liquefaction has become a large 

 industry. It has completely revolutionised the aerated water 

 manufacturing, and a large business is done in compressed 

 ammonia for the frozen meat trade, compressed oxygen and 

 hydrogen, both for lighting and inflating military balloons, and 

 nitrous oxide so familiar to those who have occasion to visit the 

 dentist. Hydrogen, as was to be expected, being the lightest 

 element, was the last of the gases to yield, and it is to Professors 

 Dewar and Ramsay that we owe much for their labors in that 

 direction. Hydrogen has not only been liquefied but frozen 

 solid. Much speculation was indulged in as to what solid 

 hydrogen would be like, it was expected by some to be metallic 

 in appearance, something like mercury, but it turns out to be 

 very much like ordinary ice, its temperature being 247° below 

 zero Centigrade, or 26' above absolute zero, it boils at 238" below 

 zero, or 35^ above absolute zero. Air at once liquefies and 

 freezes on the outside of a tube containing boiling hydrogon, the 

 exact temperature not yet being definitely settled^ owing to the 

 difficulty of constructing a reliable thermometer, but these figures 

 are very nearly true. Absolute zero being 273° Cent, below zero, 

 the certainty of there being a real zero was deduced from the 

 fact that a regular rise or fall in the temperature of a gas, pro- 

 duces a corresponding increase or decrease in the volume, and 

 when it was noted' that a gas could be doubled in volume by 

 raising the temperature from the artificial zero, of the Centigrade 

 scale, to 273° Cent, the converse result was apparent. Hence, it 

 was pointed out that if a rise in temperature of 273'' Cent., would. 



