LIQUEFACTION OF OXYGEN. 749 



legislator, can tell us with the graphic tongue of eyewitnesses, the wonders 

 of the strange lands we seek to colonize, and whose hidden secrets we seek 

 to solve ; for both have watched the colossal or fairy shapes of mountainous 

 icebergs with their changeful play of hues under the midnight sun, or the 

 mighty arch of the aurora, with its trailing fringes of incandescent colors 

 spanning through the long night of Arctic winter, the mystic sea of ice and 

 silence. Their presence, and that of the other distinguished gentlemen who 

 are announced to address us, and whose names are as familiar as household 

 words wherever the English language is known or spoken, I hail as an augury 

 of success, and I heartily join with them and you in doing honor to the 

 name and achievements of our countryman Stanley, in penetrating the 

 wilds of Africa. There is no city through©ut the whole broad Union more 

 suitable for such a meeting as the present, a city where the memory of Grin- 

 nell, the great and public-spirited merchant, is still green, and where so 

 many others, their hearts as generous as their means were large, have given 

 freely of their store to aid in Arctic discovery and iu whatever else was 

 good and noble in art and science, in love and charity. 



In closing, permit me at present to thank you all for your attention and 

 your kindly manifestation of interest in the subject, and to hope that such 

 action will be taken by Congress as will invest it with added interest in the 

 near future. 



CHEMISTRY. 



LIQUEFACTION OF OXYGEN. 

 BY M. RAOUL PICTET. 



The object which I have had in view for more than three years is to 

 demonstrate experimentally that molecular 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 attract each other, and thus do not 

 conform to this law. 



Thus, to cause experimentally the molecules of a gas to approach each 

 other as much as possible, certain indispensable conditions are necessary 

 which may be expressed thus : — 



1. To have the gas absolutely pure, with no trace of foreign gas. 



2. To be able to obtain extremely energetic pressures. 



3. To obtain intense cold, and to subtract heat at those low temperatures. 



4. To utilize a large surface for condensation at these low temperatures. 



5. To be able to utilize the rapid expansion of the gas from extreme 

 condensation to the atmosphere pressure — an expansion which, added to 

 the preceding means, will compel liquefaction. 



