704 



SCIENCE. 



[N. S. Vol. I. No. 26. 



himself this question, but he endeav- 

 oured to answer it by an appeal to experi- 

 ment. 



I should like to show j-ou Cavendish's ex- 

 periment in something like its original form. 

 He inverted a U tube filled with mercury, 

 the legs standing in two separate mercurj^ 

 cups. He then passed up, so as to stand 

 above the mercury, a mixture of nitrogen, 

 or of air, and oxygen ; and he caused an 

 electric current from a Mctional electrical 

 machine like the one I have before me to 

 pass from the mercurj'^ in the one leg to the 

 mercury in the other, giving sparks across 

 the intervening column of air. I do not 

 propose to xise a frictional machine to-night, 

 but I will substitute for it one giving elec- 

 tricity of the same quality of the construc- 

 tion introduced by Mr. Wimshurst, of which 

 we have a fine specimen in the Institution. 

 It stands just outside the door of the theatre, 

 and will supply an electric current along in- 

 sulated wires, leading to the mercury cups; 

 and, if we are successful, we shall cause 

 sparks to pass through the small length of 

 air included above the columns of mercury. 

 There they are ; and after a little time you 

 will notice that the mercur^^ rises, indica- 

 ting that the gas is sensibly absorbed under 

 the influence of the sparks and of a piece of 

 potash floating on the mercury. It was by 

 that means that Cavendish established his 

 great discoverj;- of the nature of the inert 

 ingredient in the atmosphere, which we now 

 call nitrogen ; and, as I have said, Caven- 

 dish himself proposed the question, as dis- 

 tinctly as we can do, Is this inert ingredient 

 all of one kind? and he proceeded to test 

 that question. He found, after days and 

 weeks of protracted experiment, that, for 

 the most part, the nitrogen of the atmos- 

 phere was absorbed in this manner, and con- 

 verted into nitrous acid ; but that there was 

 a small residue remaining after prolonged 

 treatment with sparks, and a final absorp- 

 tion of the residual oxygen. That residue 



amounted to about j\-^ part of the nitrogen 

 taken ; and Cavendish draws the conclusion 

 that, if there be more than one inert ingre- 

 dient in the atmosphere, at anj' rate the sec- 

 ond ingi-edient is not contained to a greater 

 extent than tstj part. 



I must not wait too long over the experi- 

 ment. Mr. Gordon tells me that a certain 

 amount of contraction has alreadj' occurred; 

 and if we project the U upon the screen, we 

 shall be able to verify the fact. It is only 

 a question of time for the greater part of the 

 gas to be taken up, as we have proved by 

 preliminary experiments. 



In what I have to say from this point on- 

 wards, I must be understood as speaking 

 as much on behalf of Professor Ramsay as 

 for myself. At the first, the work -which 

 we did was to a certain extent iadependent. 

 Afterwards we worked in concert, and all 

 that we have published in our joint names 

 must be regarded as being equalty the work 

 of both of us. But, of course, Professor 

 Ramsay must not be held responsible for 

 any chemical blunder into which I may 

 stumble to-night. 



Bj' his work and by mine the heavier in- 

 gi-edient in atmospheric nitrogen which was 

 the origin of the discrepancy in the densi- 

 ties has been isolated, and we have given it 

 the name of ' argon.' For this purpose we 

 may use the original method of Cavendish, 

 with the advantages of modern appliances. 

 "We can procure more powerftil electric 

 sparks than any which Cavendish could 

 command by the use of the ordinarj' Ruhm- 

 korfi" coil stimulated by a battery of Grove 

 cells; and it is possible so to obtain evidence 

 of the existence of argon. The oxidation of 

 nitrogen by that method goes on pretty 

 quickly. If you put some ordinarj^ air, or, 

 better still, a mixture of au' and oxygen, in 

 a tube in which electric sparks are made to 

 pass for a certain time, then, in looking 

 through the tube, you observe the well- 

 known reddish-orange fumes of the oxides 



