464 



NA TURE 



[March 19, 1903 



slightly different ; while the values for the elastic force of 

 vapour have not been corrected for the assumed barometric 

 pressure. Nevertheless, a decidedly rapid increase in the 

 humidity of the atmosphere is shown, and in considering 

 the table, it must be borne in mind that the results, if re- 

 duced to a mean temperature, would be even more striking. 

 Barnet, February 18. E. V. Windsor. 



Lagrange's Equations. 



As most of the standard treatises on dynamics contain 

 satisfactory proofs of Lagrange's equations, I do not see 

 that any useful purpose is served by proposing an additional 

 ■one. The important point is this : — That amongst the 

 numerous forms in which the kinetic energy of a dynamical 

 system can be expressed, there is only one form which can 

 foe employed in using Lagrange's equations, and that is the 

 Lagrangian form in which T is expressed as an ti-arv 

 ■quadric of velocities which are the time variations of the 

 coordinates. 



Similarly in using Hamilton's equations 



*+ 3(E + V)=o 

 dt de 



to'"' 



there is only one form, viz. the Hamiitonian form, which it is 

 permissible to use in which <2E is expressed as an «-ary quadric 

 of momenta of the same type as the coordinates of the system. 

 Now the form $(Aw,'- + But.,- + Ca> 3 ") is neiiher Lagrangian nor 

 Hamiitonian, and therefore cannot be used in either equations. 



A. B. Basset. 

 Fledborough Hall, Holyport, Berks, March 6. 



A Remarkable Meteor. 



I send an account of a meteor, to me remarkable 

 because of its extremely slow movement and also because 

 of its apparently reaching the surface of the earth, a little 

 •east of north-east of here. The " falling star " was about 

 equal in brightness to Sirius. When first it attracted my 

 attention it would be just below the cluster " Coma 

 Berenices." So slowly was it falling that I first mistook 

 it for the fixed star Arcturus, the resemblance being prob- 

 ably increased by its colour, which was reddish. It slowly 

 dropped vertically downwards, its brilliancy keeping con- 

 stant ; it left no trail. Its line of descent would make a 

 small angle with the line 53 Leonis. I watched it fall right 

 to ground — but it may not have quite reached earth, as there 

 was a rise in the ground before me. About one-third of its 

 distance from the ground it appeared to " wobble," but that 

 may have been an illusion. It fell so slowly as to take quite 

 five seconds. The lime was about 7.22 p.m. on March 15, 

 when I was a little more than a mile to the south of Basing- 

 stoke. J. E. C. Liddle. 



Fairfields, Basingstoke, Hants. 



Dawn of Modern Geography. 



In the review of my book (" Dawn of Modern Geo- 

 graphy," vol. ii.) which appeared in Nature, November 27, 

 1902, it is stated (p. 75), by way of repetition from Nature's 

 review of vol. i. of the same work, that the " revision of 

 the whole of chapter vi. of vol. i., on geographical theorv, 

 together with Mr. .Beazley's account of the history and use 

 of mediaeval maps for the whole book," was "due to Mr. 

 C. H. Coote, of the Map Department of the British 

 Museum." When this unfounded assertion was first made, 

 I wrote (with the entire concurrence of Mr. Coote) and 

 pointed out to the reviewer that he was mistaken. As the 

 misleading statement now reappears, I may say that Mr. 

 Coote never saw a line of the " Dawn of Modern Geo- 

 graphy," vol. i. — nor had I any consultation with him on 

 any point therein — until after the last corrections of proof 

 had been made, and the sheets finallv returned for press. 



C. Raymond Beazley. 



NO. I 742, VOl . 67] 



Nernst Lamps in Lanterns. 



Ii was suggested to me by a friend to use a Nernst lamp 

 in a lantern. On trying the experiment I have found that 

 a one ampere 220 volts Nernst lamp gives quite a fair result 

 in a small lantern, certainly very much better than could 

 be got with oil wicks, and when put at a small angle from 

 the horizontal the filament gives a very concentrated light. 

 For lantern purposes it would be quite possible to remove 

 the heating coil and to start the lamp by means of an alcohol 

 flame. Indeed, I think that a special Nernst burner could 

 be made for lanterns, giving a high candle power and fitted 

 with a suitable fitting, which would largely replace lime- 

 light, and it would even in many cases replace the arc 

 lamp where a powerful light was not required. There can 

 be no doubt whatever about its convenience. 



C. TURNBULL. 



Electricity Works, North Shields, March 16. 



PHOTOGRAPHS OF VOLCANIC 

 PHENOMENA. 1 



THE application of photography to the recording 

 and illustrating of volcanic phenomena has done 

 much to secure accuracy, and the avoidance of those 

 sources of error to which the students of these 

 stupendous outbursts must always be particularly 

 liable. Valuable as are the drawings made under 

 the superintendence of Sir William Hamilton for his 

 classic work, " Campi Phelgrsei," they do not carry 

 the conviction to the mind of a reader of the work 

 that actual photographs would do; while many of the 

 drawings of volcanic phenomena in less carefully 

 illustrated works are faulty and exaggerated almost 

 to grotesqueness. 



Perhaps the first serious attempts to show the 

 features of a volcanic outburst by means of instan- 

 taneous photography were those made by an enter- 

 prising photographer of Naples, during the Vesuvian 

 eruption of 1872. He obtained three photographs at 

 different hours, which illustrate very clearly the scale, 

 the principal details and the changes of phase in the 

 outburst. These photographs have since been repro- 

 duced in many geological treatises. 



During the visit of the Geologists' Association to 

 the South Italian volcanoes in 1800, a number of 

 photographs were obtained by members of the party 

 which demonstrated the value of instantaneous pho'o- 

 graphy in recording all the successive stages of an 

 outburst. Some of these photographs were repro- 

 duced in a memoir published by Dr. Johnston Lavis 

 at Naples in 1891. 



Dr. Tempest Anderson's contributions to the subject 

 appear to have begun in 1885, when he read a paper, 

 illustrated by admirable photographs, before the Geo- 

 logical Section of the British Association at Aberdeen. 

 This paper dealt specially with the extinct volcanoes of 

 Auvergne. In subsequent years, Dr. Tempest 

 Anderson has visited almost all accessible volcanic 

 districts — Italy and Sicily, the Canaries, Iceland, and 

 various parts of the North American Continent. Last 

 vear he volunteered, at his own expense, to join the 

 expedition sent out by the Royal Society to report 

 on the eruptions of St. Vincent and Martinique, and 

 the results obtained by Dr. Flett and himself have just 

 been published in the Transactions of the Royal 

 Society. 



The work before us consists of reproductions by 



1 "Volcanic Studies in Many Lands: being Reproductions cf Photo- 

 graphs by the Author of above One Hundred Actual Objects, with 

 Explanatory Notices." By Tempest Anderson, M.D., B.Sc. Lond , 

 F. G.S., F.R.G.S., A.C., Fellow of University College, London, Hon. Sec. 

 Y orVshire Philosophical Societv Pp. xxviri + 202 ; plates i. to cv 

 /London : John Murray, igo3.) Price 2i.r. net. 



