Dec. 23, 1886] 



NA TURE 



173 



Japan for that year (vol. ix. p. 40). Further, in publishing an 

 account of the horizontal pendulum seismograph, I pointed out 

 that the way to get a steady-point witli respect to one component 

 of earthquake-motion, is to pivot a body in nearly neutral equi- 

 librium, with the corresponding kind of freedom, and to use the 

 centre of percussion as the steady-point, the steadiness of the 

 steady-point being increased, if need be, by pivoting a second 

 mass there. So far as I am aware, this obvious principle was 

 first explicitly recognised and applied in my horizontal pendulum 

 seismograph ; and on this point I shall appeal from Mr. Gray of 

 18S6 to Mr. Gray of l88l :— 



" I believe the first time special attention was paid to the 

 application of this well-known dynamical principle to seismome- 

 ters is to be found in a paper communicated by Prof. Ewing to 

 the last meeting of this Society" (T. Gray, Tram. Scis. Soc. 

 yap., vol. iii. p. 5). 



(2) Mr. Gray's second charge is that I am using his vertical 

 motion seismometer without acknowledgment. I am not using 

 his instrument ; and I have acknowledged fully his service to 

 seismometry in this connection. A horizontal bar, loaded at 

 one end and held up by a spring, was used for vertical motion 

 by the British Association Committee at Comrie in 1842. In 

 1881, Mr. Giay, holding the bar up by a long spiral spring, 

 made the suspension astatic by adding a trough or tube contain- 

 ing mercury (Trans. Sets. Soc. Jap., vol. iii. p. 137). After 

 seeing this, I devised another and simpler method of making 

 the suspension astatic, and in describing it I said : — 



" At a recent meeting of the Society, Mr. T. Gray described 

 a seismometer for vertical motion, in which the problem of sup- 

 porting a heavy mass, so that it should be free to move vertically 

 and yet remain in neutral equilibrium, was for the first time (so 

 far as I am aware) successfully solved " {IhiJ. p. 140). 



My method is entirely different from Mr. Gray's. He now 

 says that it was anticipated by a paper of his, dated May 1880. 

 He did not suggest this at the time ; and, on reading the paper 

 now, I can find no trace of the alleged anticipation. In the 

 passage quoted above, and in other writings (" E.arthquake 

 Measurement," p 48 ; Natuke, vol. xxx. p. 152 ; " Encyclo- 

 pnedia Britannica," Art. "Seismometer"), I have tried to do 

 justice to Mr. Gray's priority in the solution of this problem of 

 vertical astatic suspension ; but I prefer, and use, my own later 

 solution. J. A. Ewing 



University College, Dundee, December 1 1 



How to make Colourless Specimens of Plants to be 

 preserved in Alcohol 



In your last number (p. 149) Prof. H. de Vries described 

 a valuable method for making botanical museum specimens 

 colourless ; but, as it is more important in many cases to keep 

 the original colour, you will allow me to call your attention to a 

 note in the Birichte dcr diittschen botaniscken Geselhchaft (1 886, 

 No. 8), where Dr. Tschiroh describes a method for retaining 

 the colour (green or other) on specimens preserved in spirit. He 

 discovered some time ago that tannates and colouring-matters (as 

 found in plants), with the exception of xanthophyll, form com- 

 pounds with lead and barium which are insoluble in alcohol, and 

 he based his method on this discovery. He recommends the 

 specimens to be put into solutions of compounds of lead or 

 barium before transferring them to spirit, or simply to add con- 

 centrated solutions of acetate or nitrate of lead, or chloride or 

 hydrated oxide of barium, to the spirit. I may add that I have 

 tried this method, but I have not yet got quite satisfactory 

 results. My best results were obtained by plunging the speci- 

 mens first of all into boiling water before putting them into 

 the above-mentioned mineral solutions. 



Selmar Schoni.and 



Botanic Garden, Oxford, December 18 



The Recent Weather 



My barometer, at 250 feet above sea-level, fell to 28-20 at 

 5 a.m. on December 8, and to 27'82 at 8 p.m. 



Birstal Hill, Leicester, December 18 F. T. Mott 



I GATHER from your notice of the great storm on the 8th that 

 readings of the barometer taken during its passage across the 

 country will be of some interest. I therefore place at your dis- 



posal copies of the records made at Belvoir Castle. .\n indica- 

 tion of an approaching storm was given by a falling barometer 

 on the 6th, its reading at 9 a.m. on that day being 29-380. The 

 depression increased on the 7th, reaching 28^960 ; at 9 a.m. on 

 the 8th it had fallen to 2S'2O0, and then went down rapidly, 

 until at 9 p.m. it reached its lowest point, 27 '800, the lowest I 

 have registered at this place during a period of thirty-two years. 

 During the 8th the wind was strong from the south, amounting 

 to a gale, and was accompanied with rain, o'6o being recorded, 

 but it was less violent than the indications of the barometer led 

 me to expect. That the pressure was less intense here than in 

 the storm on October 14, i88r, was evidenced by the escape of 

 timber-trees ; some 400 to 500 were blown down in 1881, and 

 not half a dozen in the woods adjacent to the Castle on the 8th. 

 Belvoir Castle is in the northern division of Lincolnshire, 

 about twenty miles east of Nottingham. The height of our 

 station, but not of the Castle, is 237 feet, lat. 52° 53' 39"-9 N., 

 long. 0° 3' 7"-4 W. William Ingram 



Belvoir 



Electrical Phenomenon 



I BEG to inclose extract from a letter just received from a 

 young friend at Yloilo, and shall be glad if you will insert it in 

 your next issue. Some of your readers may have further infor- 

 mation respecting this interesting sight. Thomas Higgin 



Ethersall, Roby, Liverpool, December 15 



" Yloilo, October I, 1886 

 " Last night a most extraordinary phenomenon was visible in 

 the heavens. About 9 o'clock the sky was perfectly clear, all the 

 stars visible, but no moon, when suddenly the wdiole heavens 

 were lit up as if by electric light, a very large globe of fire 

 became visible (about the size the moon appears when full) and 

 floated slowly northwards. I was in rather a bad position for 

 seeing where it actually went, a house being between me and 

 the horizon. This ball was followed by smaller ones, which 

 were close to the big one, and gradually got smaller, till they 

 appeared like falling stars, only they went much more slowly." 



Electricity and Clocks 



WotjLD any of your readers aid me in carrying out this idea : 

 To make the works of a small striking clock strike the hours on 

 a large bell by an electrical connection. T. Wilson 



Rivers Lodge, Harpenden, St. Albans 



BOTANY OF THE AFGHAN DELIMITATION 



COMMISSION 

 \ XT' HEN, in 1S84, it became known that the Govern- 

 * • ment intended sending a Commission to settle the 

 boundary of North-Western Afghanistan, representations 

 were made to the Marquis of Ripon, then Viceroy of 

 India, that it was desirable in the interests of science and 

 commerce that a naturalist should be attached to the 

 staff, and Brigade-Surgeon Aitchison was accordingly 

 appointed in that capacity. Certainly no better choice 

 could have been made, at least as far as botany was con- 

 cerned, because no other person had the practical know- 

 ledge of the vegetation of the region possessed by Dr. 

 Aitchison, who, moreover, is unsurpassed as a collector. 

 As long ago as 1859 he began collecting plants in the 

 Punjab, the flora of which he fully investigated ; and 

 later he collected in Scinde and some parts of Kashmir ; 

 but this was all done during his leisure hours. In the 

 winter of 1878 he accompanied the troops under the 

 command of General Sir F. Roberts in the advance 

 on Kuram, and subsequently he was attached to the 

 force as botanist, and commenced operations in April 

 1879. Botanists of all countries know full well what 

 excellent and extensive collections he made during that 

 and the following year, for, with assistance from the 

 Government of India, the results were promptly published 

 by the Linnean Society. Large and interesting as those 

 collections were, the present equals them in extent and 

 exceeds them in importance, inasmuch as Dr. Aitchison 

 paid special attention to the investigation of the many 



