774 



SCIENCE. 



[N. S. Vol. VIII. No. 205-. 



present the greatest resemblance to one 

 another. Now, in Mr. Newlands' view, the 

 fact that the eighth element resembles the 

 first suggested an analogy with the musical 

 scale, where the tones can be similarly 

 classified, each eighth note of the major 

 scale reproducing, as it were, the funda- 

 mental note. In the ordinary notation the 

 name C refers to many notes, separated 

 from each other by octaves. The analogy 

 may be regarded as fanciful, and in the 

 light of more modern work the word ' oc- 

 tave ' is here inapplicable ; and this perhaps 

 overstrained analogy did much to discredit 

 Mr. Newlands' views in the eyes of the 

 leading chemists of the day. It was not 

 until 1868, when the late Professor Lothar 

 Meyer and Professor Meudel6ef independ- 

 ently arrived at a similar arrangement, 

 that the attention of chemists was recalled 

 to the subject and the justice of Mr. New- 

 lands' ideas was acknowledged. The some- 

 what tardy award of a medal by the Eoyal 

 Society placed in its true position the work 

 of Mr. Newlands, and was regarded as an 

 act of justice by his friends. It is deeply to 

 be regretted that his recent death has re- 

 moved from our midst a man so kindly and 

 SO alive to every advance in science. 



The elements helium and argon, if they 

 be really elements and not compounds (and 

 there is no reason to doubt their elementary 

 nature), should find places in this table, 

 now known as the ' Periodic Arrangement 

 of the Elements.' And confining our at- 

 tention to only a few of the vertical col- 

 umns, their position should be for helium 

 before lithium, and for argon before potas- 

 sium, thus : 



Hydrogen 1 Helium 4 Lithium 7 



Fluorine 19 ? Sodium 23 



Chlorine 35.5 Argon 40 Potassium 39 



r Iron 56 



Manganese 55 \ Cobalt 58 \ Copper 



63.5 



Bromine 



j Cobalt 58 

 t- Nickel 59 



? Enbidium 85 



Now, we find the difference between th& 

 atomic weights of hydrogen and chlorine 

 to be 34.5 ; and between lithium and potas- 

 sium to be 32 ; also between argon and he- 

 lium to be 36. These numbers are roughly 

 of the same order of magnitude. It is^ 

 therefore, not unreasonable to suspect the 

 existence of an undiscovered element with 

 atomic weight between 19 and 23, as well 

 as of others occupying the other unfilled 

 positions in the argon group. 



It is no easy matter to hunt the earth 

 through for an unknown element. The 

 question is, where to look. And some clue 

 is necessary to guide the inquiry. At first 

 it was thought that minerals similar to 

 those from which helium had been obtained 

 might possibly yield the new element ; and 

 experiments were made, for months at a 

 time, to test the gases obtainable from al- 

 most every known mineral, but in vain, so 

 far as a new element was concerned. They 

 resulted in the discovery of many new 

 sources of helium ; but the spectrum of the 

 gas in each case exhibited no unknown lines 

 A new method of attack was then organ- 

 ized. It might be that the so-called helium 

 was really a mixture of elements, and not 

 a pure element. Now, an effective method 

 of separating from each other two gases of 

 different molecular weights, and hence of 

 different densities, is the process of diffusion. 

 From observations of the late Professor 

 Graham, of University College, London, 

 subsequently Master of the Mint, it appears 

 that lighter gases, with rapidly moving 

 molecules, will pass through a porous dia- 

 phragm, such as the material of a clay pipe, 

 more rapidly than a heavier gas, with its 

 more slowly moving molecules. An at- 

 tempt was, therefore, made to ascertain 

 whether any heavier gas could be thus sep- 

 arated from the helium obtained from min- 

 erals ; the experiments involved an enor- 

 mous amount of labor, but, in the end, no 

 gas other than a trace of argon could be 



