SOME PHYSICAL PROBLEMS 



cask show, to be sure, an adaptation of means to ends 

 on economical lines ; yet, on the other hand, it should 

 not be forgotten that the beer-cask serves its purpose 

 admirably; and, in a word, it may be said that Pro- 

 fessor Ramsay's laboratory contains everything that 

 is needed to equip it fully for the special work to which 

 it has been dedicated for some years past. In general, 

 it looks like any other laboratory glass tubes, Bunsen 

 burners, retorts and jars being in more or less mean- 

 ingless tangles; but there are two or three bits of ap- 

 paratus pretty sure to attract the eye of the casual 

 visitor which deserve special mention. One of these is 

 a long, wooden, troughlike box which extends across 

 the room near the ceiling and is accessible by means 

 of steps and a platform at one end. Through this box- 

 like tube the chief expert in spectroscopy (Dr. Bay- 

 ley) spies on the spectrum of the gas, and learns some 

 of its innermost secrets. But an even more mystify- 

 ing apparatus is an elaborate array of long glass tubes, 

 some of them carried to the height of several feet, 

 interspersed with cups of mercury and with ther- 

 mometers of various sizes and shapes. The technical 

 scientist would not make much of this description, but 

 neither would an untechnical observer make much of 

 the apparatus; yet to Dr. Travers, its inventor, it is 

 capable of revealing such extraordinary things as the 

 temperature of liquid hydrogen a temperature far 

 below that at which the contents of even an alcoholic 

 thermometer are solidified ; at which, indeed, the prime 

 constituents of the air suffer a like fate. The respon- 

 sible substance which plays the part of the familiar 

 mercury, or alcohol, in Dr. Travers 's marvellous ther- 



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