1 64 



NA TURE 



[JUxNE 13, 1907 



twe've wedges of Ugniim vilac were inserted symmttric- 

 ;illy round ihe mirror, and appear to have eliminated the 

 slight movement. 



Fifty-five photographs of the sixth, and eleven photo- 

 graphs of (he seventh, satellite of Jupiter were secured 

 with the 30-inch reflector, together with 170 photographs 

 of minor planets and comets and tn-elvc of various nebulae. 

 Of the latter, that of M 31 (.\ndromeda) and one of the 

 Ring Nebula in Lyra are especially good. 



The discussion of the photographs of Eros taken during 

 the opposition of iqoo-i was completed, and a value for 

 Ihe solar parallax, in close agreement with the previously 

 accepted value, was deduced. 



With the astrographic telescope 18S supplementary photo- 

 graphs were taken, and 133 of them w^erc passed as satis- 

 factory. Positive copies of the plates covering zones 71°- 

 74° are now completed, and of the 461 chart plates 

 necessary to cover the remaining zones, 75° to the pole, 

 seventy-five have to be repeated for the purpose of repro- 

 duction. Vol. ii. of the Greenwich .Astrographic Catalogue 

 is now complete, except for the introduction, which will 

 contain the constants for the plates, and these have now- 

 been computed. For the area included in zone 81° (from 

 6h. to 24h.) and the zones 82° to the pole, viz. 2547 square 

 degrees, the 40m. exposure plates show 75,683 star images, 

 or 297-2 per square degree; in the B.D. the corresponding 

 area (1°) includes 157 stars. .About 13,000 enlarged prints 

 of the chart plates were made during the year. 



During the period covered by the report, the sun was 

 photographed on 210 days, and for 1906, including the 

 Indian and Mauritian negatives, the daily photographic 

 record of the sun's surface was complete except for one 

 dav. Twenty-three photographs of portions of the solar 

 disc were secured with the 26-inch photographic refractor, 

 fitted wMth a negative enlarger, the scale being such as to 

 give a solar diameter of 30 inches. 



The magnetic observations were carried on as usual, the 

 principal results for the magnetic elements for 1906 being 



Mean declination 16° 3''6 W. 



Mean horizontal force 4'0I74 (in British unit*) 



I 8524 (in metric ,, ) 

 Mean dip (wilh 3-inch needles) 66° 55' 17" 



■ There were no days of " great " magnetic disturbance 

 and eight of lesser disturbance. 



The mean temperature for the year ending April 30, 1907, 

 was 5o°-5, or o°-9 above the average for 1841-1905, tne 

 highest and lowest shade temperatures recorded being 

 94°-3 (August 31) and i9°-8 (December 30) respectively. 

 Of the 4457 hours that the sun was above the horizon at 

 Greenwich, the Campbell-Stokes instrument recorded 1687 

 hours of bright sunshine. 



The total rainfall was 0-26 inch below the average for 

 the sixty-five years 1841-1905, being 23-86 inches, whilst 

 the number of " rainy days " w-as 148. 



The performance of the chronometers sent in for the 

 annual trial was hardly up to the high standard of recent 

 years, and of the fourteen pocket-chronometers submitted 

 none came up to the standard of purchase. The next trial 

 for chronometers will commence on June 15, and for 

 chronometer watches on .August 3. 



In concluding his report, the .Astronomer Roval refers 

 to the threatened danger to the astronomical efficiency of 

 the observatory occasioned by the L.C.C. generating 

 station near by, the principal point being the recommend- 

 ation of the committee appointed to consider the matter, 

 that the conditions be reviewed after the lapse of two 

 years. Experiments made last summer showed that the 

 vibrations from the present installation can be effectually 

 damped out by keeping the film of mercury in the 

 ainalgamated trough as thin as possible, but there still 

 remains the danger that these vibrations may so cause the 

 large telescopes to oscillate that delicate observations, such 

 as close double-star work, may suffer materiallv. 



A more insidious danger is that the heated gases from 

 the chimneys may affect the accuracy of star observations 

 on the northern meridian, and in that case the errors would 

 not be discovered until the observations were reduced. 

 when, possibly, it would be impracticable to repeat the 

 observations. 



NO. 1963, VOL. 76] 



Tiro H£.irr seismographs. 



"T" WO new seismographs devised by Dr. Wiechert are 

 now on sale by .Spindler and Hoyer, of GiJttingen. 

 The fact which will strike most seismologists is the magni- 

 tude of the " stationary " mass employed. The horizontal 

 pendulum uses a " stationary " mass of 17,000 kilo., 

 nearly 17 tons. The mass is composed of barytes con- 

 tained in a cylindrical sheet-iron vessel with a flat bottom. 

 Its dimensions are 2 metres In diameter by nearly 2 metres 

 in height, and, being intended to have freedom of move- 

 ment horizontally, the vessel is suspended by three iron 

 rods of 3 cm. diameter, the elasticity of which allows the 

 necessary freedom. The next striking feature is the 

 multiplication with which the thrust arm moves the 

 indicator point, and this is 2200 ! It is brought about by 

 means of four levers, multiplying 5x5x5x17^. The 

 loss owing to the inertia and elasticity of the connecting 

 system amounts to 5 per cent. only. " The instrument 

 renders specially important service in the small European 

 earthquakes where the rapid oscillations are more 

 prominent." It is clear that this statement is justified. 

 For local disturbances and extremely rapid elastic vibra- 

 tions the instrument should be of great service, but, with 

 such a multiplication, one is compelled to wonder how 

 much the machine requires to be isolated in order to avoid 

 the disturbance due to traffic. It Is not surprising to find 

 in a specimen seismogram tremors due to a gas engine 

 2^ kilometres distant. Other drawbacks to the use of the 

 pendulum are the price, 5000 marks, and the number of 

 times the paper must require to be changed. These purely 

 practical considerations must have weight with anyone 

 who has real work in view. 



The vertical seismograph has a " stationary " mass of 

 1300 kilograms, about one and a third tons. Even this is 

 great as compared with the usual one to two hundred 

 pounds. The multiplication, 160, is also large when one 

 thinks of the usual 12 to 20. " The vertical apparatus 

 often indicates the first movements of very distant earth- 

 quakes better than even the 17,000 kilo, pendulum, 

 which multiplies 2000 times ; so the Schluter result is con- 

 firmed, from which follows that in the case of first indica- 

 tions we have lo do with longitudinal movements." Thus 

 runs the prospectus. The price of this pendulum, too, 

 2800 marks, is rather prohibitive, although the workman- 

 ship in both leaves little to be desired. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



C.uiBRiDGE. — Dr. Graham-Smith, Prof. Nuttall, and 

 Prof. Woodhead have been nominated to represent the 

 University at the International Congress of Hygiene and 

 Demography to be held in Berlin in September. 



The general board of studies has approved Alexander 

 Scott for the degree of Doctor in Science. 



Profs. E. H. Liveing and H. Louis have been nominated 

 examiners in the application of science to the art of mining, 

 and Mr. C. T. Hcycock an examiner in metallurgy for the 

 diploma In mining engineering for the examination to be 

 held in the Michaelmas term, 1907. 



The Balfour studentship will be vacant at Michaelmas 

 next. The names of applicants, together with such in- 

 formation as they may think desirable, should be sent 

 on or before October i lo the secretary, J. W. Clark, 

 Registry of the Lniverslty, Cambridge. The studentship 

 is of the net annual value of 200I., or such larger sum as 

 the University may from time to time determine. The 

 student need not be a member of the University, and 

 during his tenure of the studentship is required to devote 

 himself to original biological inquiry. 



The Vice-Chancellor announces that the advisory com- 

 mittee of the Colonial Oflice for the tropical diseases re- 

 search fund recommends that a grant of 100!. for two 

 years should be made from the fund to assist in establish- 

 ing a research studentship in medical entomology in Cam- 

 bridge, and that Lord Elgin Is prepared to approve of the 

 proposal. Candidates for the studentship are requested to 

 send in their applications to Prof. N'uttall, 3 Cranmer 

 Road, Cambridge, on or before Monday, June 17. 



