1898] Liquid Hydrogen. 85 



Gray Fork-tailed Petrels {Pceanodrouia fiircata, Gmei.) were seen 



resting on the bosom of the water, also an occasional Murre flying 



past and three Terns hovering about over head. 



The Terns were particularly beautiful : the head was black 



on the top, the back ashy grey, the breast pure white, the tail 



forked. 1 was attracted to them by the cry. I was further 



unabled to examine this tern, as one example came on board 

 towards night-fall, and I had it in my hand. There was a white 



mark along the crown of the head, and 1 would have pronounced 

 it the Aleutian Tern {Sterna aleutica, Baird), except that th^ 

 bill was orange on the under mandible, and Coues says the bill 

 of that species is black. The feet were also orange : the hallux 

 small and well set behind the tarsus. It was seemingly a 

 young bird and tired, and so had sought a resting place on the 

 deck of the vessel. I took it down to the cabin and put it on 

 the table, where it dressed its feathers with its bill and pecked 

 at my finger. I then released it. Away it soared, far up into 

 the air, the wind and the waves congenial, far distant from the 

 land. 



Andrew Halkett. 

 Ottawa, 30th June 1898. 



LIQUID HYDROGEN 



A notable event in the history of chemistry is being 



chronicled in the scientific journals. At the meeting of the 



Royal Society (England) on the 12th may last. Professor 



Dewar, a chemist eminent by reason of his successful research 



work at low temperatures, announced that by means of special 



apparatus, a pressure of 180 atmospheres and a temperature of 



-210 degrees C. he had liquefied hydrogen. It has only been 



within the the last few years that oxygen, nitrogen and air have 



been liquefied ; the liquefication of hydrogen and helium, the 



last of the so-called permanent gases, is now an established 

 fact. 



The apparatus for this achievement, says Dr. Dewar, " took 



