May 2. 1895] 



XATURE 



uhcre there uas not excesaivu moisture, might retain 

 their germinati\c power for an almost indefinite period ; 

 and the fatt that plants previously unknown in a locality 

 often spring up where excavations have been made, bear 

 out this assumption. The same thing happens in arable 

 land, should the farmer plough deeper than usual ; and 

 deeper tillage, which would otherwise be beneficial, is 

 often avoided on this account. A careful writer like 

 Lindlcy states, though without qualification, that he had 

 raspberry plants raised from seed taken from the stomach 

 of a man, whose skeleton was fountl thirty feet below the 

 surface of the groimd. Judging from coins found at the 

 same place, the seeds were probabh 1600 or 1700 years 

 old. One more example of seeds germinating that are 

 supposed to have been buried some 1 500 to 2000 \ears. 

 About twenty years ago, on the remo\al of a quantit\' of 

 slack of the ancient silver mines of Greece, several plants 

 sprang up in abundance previously unknown in the 

 locality. Among these was a species of Glauciuiii. which 

 was even described as new ; and it is suggested that the 

 seed may have lain dormant for the long period indicated. 

 Ijiit there is not the amount of certainty about any of 

 these assumed very old seeds to convince the sceptical or 

 to establish a fact. It remains yet for somebody to 

 institute and carry out careful investigations where 

 excavations are being made. 



W. ISoTTixr, Hemsi.kv. 



TERRESTRIAI. HKLIi 'M{.'). 



\ r the meeting of the Royal Society on Thursday last 

 -^'*- (April 25), two papers dealing with the nature of 

 the gas from uraninite were presented. We print both 

 papers in full. 



On a Gas showi.nc the Si'KCTRr.v of Hei.U'm. the 



RErOTED CAUSE OF D3, ONE OF THE LiXES IN THE 

 SVECTRUM OF THE Sin's CHROMOSPHERE.' 



In the course of investigations on argon, some clue was sought 

 for, which would lead to the selection of one out of the almost 

 innumerable compounds with which chemists are acquainted. 

 « illi which to attempt to induce argon to combine. .\ pa)K.T In 

 W. \- . Uillebrand, "On the Occurrence of Nitrogen in Uraninite. 

 iVc." (ButUtin of t/u U.S. Giolo^i,al Simvy, No. 78, p. 43). 

 to which Mr. Miers kindly directed my attention, gave the desired 

 clue. In spite of Hillehranirs |xisitive proof that the gas he 

 obtained by boiling various samples of uraninite «ith weak 

 sulphuric acid was nitrogen (p. 55) — such as formation of anunonin 

 on sparking with hydrogen, analysis of the platinichloride. 

 vacuum-tube S])ectrum, cVc. — I was sceptical enough to doubt that 

 any conqxiund of nitrogen, when boiled with acid, would yield 

 tree nitnigcn. The result has justified the sceptici:?m. 



Tlie mineral employed was cleveite, essentially a uranate I'f 

 lead, containing rare earths. On lioiling with weak .sulphuric 

 acid, a considerable quantity of gas was evolved. It was sparked 

 with oxygen over .soda, so as to free it from nitrogen and all 

 known gaseous bodies except argon : there was but liitle con- 

 traction ; the nitrogen removed may well have been introduced 



'in air iluring this preliminary experiment. The gas was trans- 



ired over mercur}", and the oxygen absorbed by potia.ssiuni 

 I yrogallate ; the gas was removed, washed with a trace of lK)ile<l 

 water, and dried by admitting a little sulphuric acid into the 

 lulie containing it, which stood over mercurj-. The total amount 

 was some 20 c.c. 



Several vacuum-tulies were filled with this gas, anil the 

 sjH-ctrum was examined, the sixctrum of argon lieing thrown 

 simultaneously into the spectro.scojie. It was at once evident 

 I bat a new gas was present along with argon. 



fortunately, the argon-tuln.- was one which hail been maile to 

 Uy whether magnesium-poles would free the argon from all 

 traces of nitrogen. This it did ; but liyilrogen w,is evolved froui 

 the magnesium, so that its >jiectrinn was distinctly visible. 

 ^^lreover, magnesium usually contains sodium, and the I) line 

 was also visible, thovigh faintly, in the argon-tube. The gas 



1 PreliniiiKiry Xole. h\ I'r.jf. William R.-ims.-iv . I- R..^. 

 NO. I 33 I, VOL. 52"] 



from cleveite al.so showed hydrogen lines dinil)-, probably 

 through not haWng \>een filled with completely dried gas. 



On conqwring the two sjx-ctra, I noticed at once that while 

 the hydrogen an<l argon lines in both tubes accurately coincided, 

 a brilliant line in the yellow, in the cleveite gas, was nearly 

 iut not i/uife coincident with the sodium line D of the argon- 

 tube. 



Mr. Crookes was .so kind as to measure the wave-length of 

 this remarkably brilliant yellow line. It is 587 -49 millionths of 

 a millimetre, and is exactly coincident with the line D3 in the 

 solar chromosphere, attributed to the .solar element which has 

 been named helium. 



Mr. Crookes has kindly consented to make accurate measure- 

 ments of the position of the lines in this spectrum, which he will 

 publish, and I have placed at his disposal tubes containing the 

 gas. I shall therefore here give only a general account of the 

 appearance of the spectrum. 



\\Tiile the light emitted from a Pliickers tube charged with 

 argon is bright crimson, when a strong current is passed through 

 it, the light from the helium-tube is brilliant golden yellow. 

 With a feeble current the argon-tube .shows a blue-violet light, 

 the helium-tube a steely blue, and the yellow line is barely visible 

 in the spectroscope. It appears to require a high temperature 

 therefore to cause it to appear with full brilliancy, and it may be 

 supposed to be part of the high-temperature spectrum of 

 helium. 



The following table gives a qualitative comparison of the 

 spectra in the argon ' and in the helium-tubes. 



Red..,', ^., 



irgoii-tiibc. 



I.St triplet. 

 2nd pair. 

 Faint line. 

 Stronger line. 

 Brilliant line. 

 Strong line. 

 Moderate Line. | 



Red- J 

 orange I 



, , I Faint line. 



Orange|.j.^ij^,^j 



'^^^"g'^-.fPair. 

 yellow ( 



\'ellow Absent. 



dreen 



1st triplet. 

 2nd pair. 

 Faint line. 

 Stronger line, 

 null line. 

 \'ery dim line. 

 Moderate line 



Heh'iim-tiibe. 



Equal in intensity^ 



Weak in helium. 

 Equal in intensity. 



I Faint line. 

 (Iriplcl. 



Pair, 



Brilliant. 



7 lines. 



, . 1 5 lines, 



(■reen- -ii . 

 -I Absent. 



(^Absent. 

 .\bsent. 

 1 3 lines, strong. 



"°'^' I2, fairly strong. 

 Absent, 

 Absent, 

 I Violet pair. 

 Single line. 

 Triplet. 

 Triplet. 

 Pair.- 



blue 

 Blue 

 Blue 



Violet i 



7 lines. 

 5 lines. 

 Faint. 

 Brilliant. 



8 lines. 



Barely visible, if in 

 deed present at all 

 2, fairly .strong. 

 Bright line. 

 4 bright lines, 

 Violet [xiir. 

 Single line. 

 Triplet. 

 Triplet. 

 Pair. 



^=587-49 

 (the helium line, D3I- 

 Equal in intensity- 



In helium only. 



Equal in intensity.^ 

 \ln helium only 

 Equal in intensity. 



It is tol)e noticed that argon is present in the helium-tube, and 

 by the use of two coils the spectra could Iw made of equal 

 intensity. But there are sixteen easily visible lines present in the 

 helium-tube only, of which one is the magnificent yellow, aiid 

 there are two red lines strong in argon and three violet lines strong 

 in argon, but barely visible and doubtful in the helium-tube. This 

 would imply that atmospheric argon contains a gas absent from 

 the argon in the helium-tube. It may be that this gas is the 

 cause of the high density of argon, which would place its atomic 

 weight higher than that of |X5ta.ssium. 



It is idle to speculate on the iiro|x;rties of helium at such an 

 early stage in the investigation ; but I am now prejiaring fairly 

 large i|uantities of the mixture, and hope to be able before long to 

 give data respecting the density of the mixture, and to attempt 

 the separation of argon from helium. 



' The tube ihcn usttl was the one with ■which Mr. Crookes' measurements 

 of the argon -spectrum were made. It contains absolutely pure atmospheric 

 argon. 



