12 



NA TURE 



[November i, 1894 



of masses. In the course of a communicalion which I made to the 

 Physical Socieiy of London, at their last meeting, I appealed to 

 the Fellows present lo supply me with the missing phrase. In the 

 discussion which iollovved the paper, thi<; matter was only inci- 

 dentally referred to : but, aUhoagh I think that there wa4 a 

 general agreement as lo the want, unfortunately the meeting 

 closed without coming to any conclusion as to the best method 

 of supplying the deficiency. 



Will some of your readers help me in this matter? 



12 Park Side, Cambridge. E. H. GRIFFITHS. 



The Swallowing of One Snake by Another. 



The snake incident, described in Nature, October 25 last, 

 page 620, as having occurred in the reptile-house in the Zoo- 

 logical Society's menagerie, recalls to my mind two similar 

 cases, recorded in the same periodical, vol. xxx. July 3, 1884 

 (".\ Cannibal Snake," by E. H. Evans), and July 31, 1SS4 

 (" The Swallowing of One Snake by -Another," by C. K. Osten- 

 Sacken). The first case was observed in Java, the other was wit- 

 nessed by me in Washington, D.C. In the latter case one of the 

 snakes, although three-quarters of its length had already been 

 engulphed in the other, succeeded in getting out, apparently 

 unhurt, as it remained alive and well in the cage a long time 

 afterwards. 



In the Figaro, July 26, 1894, I found still another instance 

 of the same kind, which happened in the Jardin d'.Vcclimata- 

 tion in Paris. A large snake, while attempting to swallow a 

 rabbit, was interfered with by another one, and passed with the 

 rabbit into the body of its comrade of captivity ("L'un des 

 deux passa a la suite du lapin dans le corps de son camarade de 

 captiviie"). C. K. Oste.n-Sacken. 



Heidelberg, Germany, October 28. 



O.V RECENT RESEARCHES IN THE 

 INFRA-RED SPECTRUM} 



T PRESENTED to the Association in 1882, at 

 *■ Southampton, an account of some researches made 

 by means of the bolometer, in the infra-red spectrum, 

 formed by a glass prism ; but though these labours have 

 continued wuh occasional intermission during the past 

 twelve years, it is for reasons, which will be explained 

 later, only within the past three years that any notable 

 advance has been made, and only within the past twelve- 

 month that such a measure of success has been attained 

 as justifies the present communication. 



This is not the time to give any historical account 

 of discovery in the infra-red, but all those interested 

 in the subject know that the first investigator here 

 was Sir William Herschel, whose observations con- 

 sisted essentially in finding that there was something 

 which the eye could not see in a region which he pro- 

 po-cd to call the " thermometric spectrum." His dis- 

 tinguished son. Sir John, made a curious anticipation of 

 later discovery by indicating, though crudely, that this 

 invisible heat was not uniformly distributed, and a similar 

 conclusion was reached in an entirely different manner, 

 through the thermopile, by the too early lost iMelloni. So 

 ignorant, in spite of these investigations, of those of the 

 elder Draper and of the elder IJecqucrel, were we till 

 lately, that when,'|uite within my own recollection and 

 that of most of you, Lamansky in 1871 published, from 

 his observations with the thermopile, a crude little illus- 

 tration showing three inequalities in the energy curve, 

 universal attention was e.tciled by it among those 

 interested in the subject. 



Among other minds my own then received a stimulus 

 which turned it in this direction, and having, as it seemed 

 lo me, exhausted the capacities of the thermopile, I 

 invented an instrument for continuing the research, 

 which was afterwards called the bolometer, and with 

 which, in |8<|, at an altitude of 13,000 feet upon Mount 

 Whitney, I found spectral regions hitherto unreached, 

 and whose existence had not been suspected. 



> A paprr rcirl lo Section A of the Itrilii,!) Association, at the Oxford 

 nc ting on AuKutt 11, hy .S. P. l.angley. 



NO. 1305. VOL. 51] 



I returned with a strong impression of the prospective 

 importance of this discovery, and laboured at the .Alle- 

 gheny Observatory in improving all portions of the new 

 method of research, especially of the bolometer and its 

 adjuncts, with the twofold object of obtaining greater 

 sensitiveness to heat, and greater precision in fixing the 

 exact point in the spectrum where the change of heat 

 originated. With the former object such a degree of 

 sensitiveness was at that time reached, that the bolometer 

 indicated a change of temperature of ,,^|iV,,jo of <i degree 

 Centigrade, and with the latter, such precision that it was 

 possible to fi.x the relative position of a line, not 

 merely with a possible error of a considerable fraction 

 of a degree, such as Lamansky's determination is 

 evidently subject to, but with a certainty that the error 

 would be within a minute of arc. The range of the 

 apparatus in wave-lengths was almost unlimited as com- 

 pared with any other process, and both its sensitiveness 

 and its possible precision seemed to be at that time 

 notable as compared with previous methods, for a great 

 advance was made on anything done before with the 

 thermopile, when the presence of the well-known " D " 

 line of sodium was rendered sensible (though barely 

 sensible), even as a siiis^le line, by the change of tem- 

 perature. The sensitiveness was also, as has been said, 

 accompanied with the possibility of unusual precision. 

 The results of this labour were laid before the British 

 Association in the communication already alluded to, 

 and which exhibited ten or twelve inflections of the 

 curve in the portion till then almost unknown, which 

 extends from a wave-length of of \y. to a wave-length of 

 nearly jw, at which point the glass prism then used 

 became wholly opaque to radiation. The positions of 

 these inflections were fixed with a precision quite impos- 

 sible to the thermopile, but this exactness was only 

 obtained in practice by a process so slow as to be almost 

 prohibitory ; and with this apparatus the writer person- 

 ally made in those earlier years such a number of obser- 

 vations as he h.irdly likes to recall, so disproportionate 

 did the labour inherent in this method seem to the final 

 result. 



The justification of this labour seemed to lie in the fact 

 that it does not appear that photography has ever ren- 

 dered anything much below a wave-length of i^ -any- 

 thing, at least, which has been reproduced for publication 

 in a way which gives confidence that we are in touch 

 with the original. The processes which involve the use 

 of phosphorescent substances have given some indications 

 of lines considerably below i/j, but it is safe to state that 

 the work which has just been referred to as communi- 

 cated to this .Association in 1882, presents almost the only 

 indications which we have possessed, even up to the 

 present time, about the lower infra-red solar spectrum. 



Now the curve which was given, even in the later 

 Allegheny observations made with the rock-salt prism, 

 contained but a dozen inflections below the wavelength 

 of l'5^, and these inflections, with their correct prismatic 

 and wave-length positions, represent, I think, most of our 

 present knowledge in these regions even today. 



To understand the method by which there were attained, 

 but only at this great cost of labour, results till then un- 

 reached, it may be repeated that the bolometer had been 

 rendered more sensitive than the thermopile, but that it 

 was capable of being pointed and its position in the 

 spectrum being measured, only by a tedious process 

 which has been exchisively used till lately (but which that 

 presently lo be described advantageously replaces). 

 Whichever process is used, when the bolometer thread 

 touches a cold line in the spectrum (since what is black 

 to the eye is cold to it), a larger current llows through the 

 galvanometer, and the spot of light marking the needle's 

 motion is deliecled through a certain number of degrees. 

 From this ])oint forward, the new process, whose re- 

 sults I am about to have the pleasure of bunging before 



