JlSE 28, 1895.] 



SCIENCE. 



709 



mospheric nitrogeu. I have here an appa- 

 ratus of a somewhat rough description, 

 which I have employed in experiments of 

 this kind. The boiler employed consists 

 of an old oil-can. The water is applied to 

 it and drawn from it by coaxial tubes of 

 metal. The incoming cold water tlows 

 through the outer annulus between the two 

 tubes. The outgoing hot water passes 

 through the inner tube, which ends in the 

 interior of the vessel at a higher level. By 

 means of this arrangement the heat of the 

 water which has done its work is passed on 

 to the incoming water not yet in operation, 

 and in that way a limit'Cd amount of heat 

 is made to bring up to the boil a very much 

 larger quantity of water than would other- 

 wise be possible, the greater part of the 

 dissolved gases being liberated at the same 

 time. These are collected in the ordinarj^ 

 waj-. What you see in this flask is dis- 

 solved air collected out of water in the 

 course of the last three or four hours. Such 

 gas, when treated as if it were atmospheric 

 nitrogeu, that is to say after removal of the 

 oxygen and minor impurities, is found to 

 be decidedly heavier than atmospheric nitro- 

 gen to such an extent as to indicate that 

 the proportion of argon contained is about 

 double. It is obvious, therefore, that the 

 dissolved gases of water form a convenient 

 source of argon, by which some of the labor 

 of separation from air is ob\'iated. During 

 the last few weeks I have been supplied 

 from Manchester by Mr. Macdougall, who 

 has interested himself in this matter, with 

 a quantity of dissolved gases obtained from 

 the condensing water of his steam engine. 



As to tlie spectrum, we have been in- 

 debted from the first to Jlr. Crookes, and 

 he has been good enough to-night to bring 

 some tubes which he will operate, and 

 which will show you at all events the light 

 of the electric discharge in argon. I cannot 

 show you the spectrum of argon, for unfor- 

 tunately the amount of light from a vacuum 



tube is not sufficient for the projection of its 

 spectrum. Under some circumstances the 

 light is red, and under other circumstances 

 it is blue. Of course when these lights are 

 examined with the spectroscope — and they 

 have been examined by Mr. Crookes with 

 great care — the iliflFerences in the color of 

 the light translate themselves into different 

 groups of spectrum lines. We have before 

 us Mr. Crookes' map, showing the two 

 spectra upon a very large scale. The upper 

 is the spectrum of the blue light ; the lower 

 is the spectrum of the red light ; and it will 

 be seen that they differ very greatly. Some 

 lines are common to both ; but a great many 

 lines are seen only in the red, and others 

 ai"e seen only in the blue. It is astonishing 

 to notice what trilling changes in the con- 

 ditions of the discharge bring about such 

 extensive alterations in the spectrum. 



One question of great importance, upon 

 which the spectrum throws light is : Is the 

 argon derived by the oxygen method really 

 the same as the argon derived bj' the mag- 

 nesium method? Bj* Mr. Crookes' kind- 

 ness I have had an opportunity of examin- 

 ing the spectra of the two gases side by side, 

 ivnd such examination as I could make re- 

 vealed no difference whatever in the two 

 spectra, from which, I suppose, we may 

 conclude either that the gases are absolutely 

 the same, or, if they are not the same, that 

 at any rate the ingredients by which they 

 differ cannot be present in more than a 

 small proportion in either of them. 



My own observations upon the spectrum 

 have been made principally at atmospheric 

 pressure. In the ordinary process of spark- 

 ing, the pressure is atmospheric, and if we 

 wish to look at the spectrum we have noth« 

 ing more to do than to include a jar in the 

 circuit and to put a direct vision prism to 

 the eye. At my request, Professor Schuster 

 examined some tubes containing argon at 

 atmospheric pressure prepared bj* the oxy- 

 gen method, and I have here a diagram of 



