February 25, 19 15] 



NATURE 



709 



diagram which he publishes in his communication. 

 He shows further that this fluctuation in brightness 

 was closely associated with the direction of the comet's 

 tail in relation to the sun. • 



Magnitude Error in Parall-ax Determinations. — 

 In the January number of the Astro physical Journal 

 Prof. Kapteyn describes a ver\- ingenious device for 

 avoiding systematic error depending on magnitude in 

 the measurement of stellar photographs. If this 

 error could be removed, Prof. Kapteyn does not see 

 why it should not be possible — in the average of a 

 sufficient number of observations or of a sufficient 

 number of stars — to be able to reach almost any 

 desired accuracy. The method of removing the error 

 looks surprisingly simple, and seems to contain a 

 complete solution of the problem. The idea is to 

 obtain stellar photographs on which the stars of all 

 different degrees of brightness are represented by 

 perfectly equal images. To secure this two photo- 

 graphs of the same star region are required. The 

 first photograph is taken when the plate is placed 

 slightly within the principal focal plane of the tele- 

 scope. On this plate it will be found that after de- 

 velopment all the stars will be represented by circles 

 of the same diameter but of different densities depend- 

 ing on the brightness of the stars. This negative is 

 now replaced in the telescope exactly in its former 

 position, the cones of light of the several stars falling 

 on it as before. A second photograph — the main plate 

 — is now taken in focus. It will be seen that the light 

 of a bright or faint star before it can reach the main 

 plate will have to pass through a den<;e or faint film 

 screen respectively. In this way the images are 

 brought nearer to equality. At present only one test 

 has been made, and that not under the best conditions, 

 but the results are certainly v'ery promising. 



Radiometric Measurements of no Stars. — A com- 

 parison of stellar radiometers and radiometric measure- 

 ments on no stars is the title of a paper by Mr. 

 \V. W. Coblentz, which appears in the Journal of the 

 Washington .\cademy of Sciences for January 19 

 (vol. v., No. 2). This paper, as stated, is only a brief 

 summan,- of one to appear in the Bulletin of the 

 Bureau of Standards. Reference is first made to ex- 

 periments which show that there is little difference 

 in the radiation sensitivity of stellar thermo-couples 

 constructed of bismuth-platinum and thermo-couples of 

 bismuth-bismuth plus tin allo}*, which have a 50 per 

 cent, higher thermo-electric power. A stellar thermo- 

 couple was found more sensitive than a bolometer, 

 and greater improvements are expected in the former 

 than in the latter. Measurements were made of 

 the bright and dark bands of Jupiter, the rings of 

 Saturn, a planetarv- nebula, and 105 stars. Quantita- 

 tive measures were made on stars down to 5-3 mag- 

 nitude, and high-grade qualitative measures on stars 

 down to 67 magnitude. Red stars were found to emit 

 from two to three times as much total radiation as 

 blue stars of the same photometric magnitude. 

 Measurements were also made of the transmission 

 of the radiations from stars and planets through an 

 absorption cell of water. Of the total radiation 

 emitted blue stars had about twice as much radiation 

 as yellow stars, and about three times that of red 

 stars in the visible region of the spectrum. The object 

 of the investigation was primarily to form some esti- 

 mate of the sensitivity required to be able to observe 

 the spectral energy curves of stars, and the author was 

 led to conclude that by usine a 7-ft. mirror and 

 increasing the sensitivity of his present radiometer 

 twenty times the required sensitivity could not only 

 be reached but was possible. 



NO. 2365, VOL. 94] 



Deter-mination of Time. — Under the title "JDeter- 

 minaci6n de la Hora por .Alturas absolutas, corre- 

 spondientes e ig^ales de distintas Estrellas," Sr. 

 Carlos Puente, of the .Astronomical Observatory of 

 Madrid, has published a very full account of the best- 

 known methods of determinmg time by means of alti- 

 tude obser\ations of the sun and stars. The work 

 consists of four chapters, of which the first deals 

 briefly with the general principles of astronomical 

 time, with its continuous record and methods of trans- 

 1 mission. The other chapters discuss in detail the 

 ! theorv- and practice of time determination, first by the 

 observation of absolute altitudes based largely on a 

 , method developed by Prof. Donner, of Helsingfors, 

 : next by equal altitudes of the same object on both 

 j sides of the meridian, and thirdly by the observation 

 j of two stars at the same altitude. Each method is 

 j illustrated by practical examples, and the accuracy 

 ! of the results is estimated. .At the end of the work a 

 j number of useful numerical tables are given. 



! THE SEA FISHERIES AND THE WAR. 



I A FTER some six months of the war we can attempt 

 ^"^ to make estimates of its effects upon British 

 industries, and anticipations of the future, with some 

 degree of confidence. This is fairly easy with respect 

 ; to the fisheries : the industry is being closely studied, 

 I and, unlike most, it is the object of both scientific and 

 , statistical investigation. The situation at present is 

 I one of extraordinary interest, even from a strictly 

 I scientific point of view. The enormous restrictions on 

 j fishery constitute (unhappily) an experiment on the 

 j grand scale, and since the scientific study of the 

 industn,- has not altogether been allowed to drop 

 interesting results should be forthcoming. The statis- 

 tics of the next year or two will be of much value, 

 in showing to what extent commercial exploitation of 

 the North Sea depletes the natural resources of that 

 fishing area. Amidst the distractions of the present 

 ; time this question is not being neglected. 

 I The industry itself has naturally suffered to a great 

 extent. At the beginning of the war it was almost 

 completely disorganised, .\bout the beginning of 

 . August practically the entire Grimsby trawling fleet 

 I was laid up, and deep-sea fishing had almost been 

 } suspended; but at the beginning of October 500 

 I Grimsby vessels had resumed fishing. Exf>orts of 

 I both fresh and cured fish fell off to a great extent 

 i because of the loss of German trade. That country 

 i took more than 90 per cent, of the fresh fish exported 

 I from Britain, and about 43 per cent, of the pickled 

 j herrings. Russia took about the same proportion of 

 ] our cured fish. This trade ceased, and at the begin- 

 I ning of .AugTJSt the stock of cured herrings held in 

 j Britain was estimated at 300,000 barrels, or about 

 j 37,500 tons in weight. How this part of the fishing 

 industry has been affected since then it is still impos- 

 j sible to say. The quantities of fish landed also under- 

 went a great decrease ; in September, for instance, 

 this decrease was about 38 per cent, of the quantity 

 landed in the corresponding month of 1913. This 

 falling-off has been due to several causes. A con- 

 siderable number of trawlers were commissioned as 

 mine-sweepers and patrol vessels — ^how many it is 

 impossible to say. On .August 18 the Navy List con- 

 tained the names of 107 vessels, and two months later 

 at least 200 of the total Grimsby fleet of 600 ships had 

 been commissioned, or were waiting to be so. In 

 itself this withdrawal of the best vessels, for defence 

 purpKJses, led to a marked diminution of fishing; and 

 since a large number of the best men were also taken 

 there was a great shortage of officers, so that many 



