November 27, 1902] 



NA TURE 



91 



Comet 1902 c (Grigg). — A communication from Mr. P. 

 Baracchi, director of the Melbourne Observatory, to No. 3S2S 

 of the Astronomische Nachrichten states that a search was made 

 for this comet on the first available evening after Mr. Grigg's 

 announcement of its discovery, but without success ; nor has the 

 comet been found by any of the Australian observatories. This 

 may be accounted for by the prevalence of bright moonlight on 

 the available nights and by the statement of Mr. Grigg that the 

 object was an extremely faint one. 



Enclosed with this communication is a list of the observations 

 made by the discoverer. These observations state that the 

 comet, when first seen, appeared as a faint nebula and was about 

 twice the diameter of Jupiter, the atmosphere never being quite 

 clear. Fourteen observations were made between July 23, when 

 the comet was first seen, and August 3, but after the latter 

 date, bad weather and bright moonlight prevented any further 

 observations. 



The instrument used was a 3|inch refractor, and the N.A. 

 clock stars 0, y and 5 Virginis, and v Virginis, were observed 

 as "near" stars, the apparent position of the last named being 

 taken as lih. 40m. 52s. + 1° 4''5- 



From the observations made on July 24, 27 and 30, Mr. Grigg 

 has computed the following corrected elements : — 



T = 1902 June 20-33 G.M.T. 



a = 301 4<i'I 



fl =217 31-4 



i = 16 42-9 



log q = 976618. 



The position for August 3 as computed from these elements 

 differs by + im. 36s. and + 4' from the observed position 

 on that date. 



The computed position at perihelion was a — 113° 34', 8 = 

 + 15" 23', about'io" north of Procyon, the apparent distance from 

 the sun being 25" E. , 6° S. The longitude of the comet from 

 the sun would then increase, and the comet would pass through 

 Cancer towards Regulus until it reached Virgo at the time of 

 its discovery by Mr. Grigg. 



Apparent Deviations from Newton's Law of Gravi- 

 tation. — In a paper read at the Gottingen meeting of the 

 Astronomische Gesellschaft on August 4, Herr Peter Lebedew 

 reviewed the various theories which have ever been proposed to 

 account for the apparent contradiction to the law of gravitation 

 as observed in the repulsion of comets' tails from the sun, and 

 he finally accepts the theory of Kepler, which attributes the 

 repulsive force to solar radiation. 



The author stated that he had recently confirmed the quanti- 

 tative relation expressed in the formula for this repulsion, due 

 to Maxwell and Bartoli. 



For a spherical body, the diameter of which is great as com- 

 pared with the wave-lengths of the solar radiation, the resulting 

 action (F) is expressed, in gravitational units, by the formula 



10,000 rS 



where r is the radius in centimetres and S is the density 

 of the body as compared with that of water. For dust 

 particles, the diameters of which are comparable with the wave- 

 lengths of the solar radiation, the above relation does not hold 

 good. 



This relation explains the varying behaviour of different parts 

 of a comet, for it is obvious that, in a cometary nucleus made 

 up of meteorites of various dimensions and densities, we should 

 expect varying values of F. 



Total Light of all the Stars. — Mr. Gavin J. Burns 

 contributes to No. 3, vol. xvi. of the Astrophysical Journal an 

 interesting account of some results he has obtained whilst 

 attempting to estimate the total light of all the stars. 



In the first place, he determined the relative brightness of 

 different parts of the sky by observing these different parts 

 through varying thicknesses of ordinary clear glass, and then 

 determining what proportion of the total incident light was 

 transmitted by a unit thickness of glass. He found that the 

 luminosity of the Milky Way varies from two to three times the 

 luminosity of the rest of the sky. 



Secondly, he compared the luminosity of the stars with that of 

 the normal sky by the method of putting the star image out of 

 focus until its apparent brightness was equal to that of the sur- 



NO. 1726, VOL. 67] 



rounding sky ; by this process he deduced, from the mean of 

 several independent observations of various stars, that half a 

 square degree of non-Galactic sky gives as much light as a fifth- 

 magnitude star. From further observations, Mr. Burns found 

 that, given a perfectly black background, stars as faint as the 

 eighth magnitude would be readily visible. 



WEST INDIAN VOLCANIC ERUPTIONS. 



A S a panacea for much ignorance, the subtle fluid of Franklin' 

 ■^ stands next to superstition. If you cannot explain the 

 angry workings of a volcano by a Pluto, a Vulcan or the smug- 

 glings of the damned, tell the man in the street that it is due to 

 electricity and he is happy. At the present moment, in seven- 

 teen columns of the Revue Scientifique of September 6, M. 

 Arthur Tarquin offers to the world an electrical theory of 

 volcanic action which, to a great extent, is novel. At the outset 

 we are told that the earth is entirely governed by the sun, and 

 as its energy varies so will various activities on the earth vary. 

 In establishing such a connection for volcanic activity, M. 

 Tarquin, however, poses as a special pleader. In Tokio, for 

 example, he says that earthquakes (sic) are most numerous 

 about the times when sun-spots are at a maximum and at a 

 minimum. Dr. E. Naumann, who examined the earthquake 

 registers of Japan, however, failed to find such a connection., 

 and others who have worked with materials relating to other 

 countries have arrived at similar conclusions. As another 

 example of incompleteness in statement, we are told that at the 

 " moment pricis "of the eruption in Martinique, with a mathe- 

 matical exactitude magnetic needles at observatories throughout 

 the world were violently disturbed. Even if we admit this to 

 have been the case, we fail to see why similar phenomena were 

 not observed with the more violent eruption which took place 

 the day previously in St. Vincent. 



As solar energy penetrates denser and denser layers of the 

 earth's atmosphere, the same becomes warmer and warmer ; 

 why, therefore, asks M. Tarquin, should not the internal heat 

 of ihe earth be explained by similar reasoning? This heating 

 he apparently regards as the result of an increasing resistance to 

 the passage of electricity. The oceans are regarded as vast 

 accumulators. Electric potential is greater where ocean currents 

 meet with obstacles, as, for example, where the Gulf stream passes 

 the Antilles, and it is, therefore, in such places where volcanic 

 activity is pronounced. 



So convinced was M. Tarquin of the truth of his theory 

 that he brought the same to the notice of M. le Ministre des 

 Colonies, but it apparently received but small consideration. 

 An official commission was sent to Martinique, but it neither 

 foretold the eruption of July .9 nor that of August 27. On the 

 contrary, it concurred in the return of the inhabitants to their 

 deserted homes and the establishment of brigades of soldiers at 

 Morne Rouge and other places, whilst the chief of the scientific 

 mission issued in the official journal a letter assuring the in- 

 habitants of safety. 



This advice M. Tarquin holds to have been based on 

 classical but false hypotheses respecting the cause of volcanic 

 activity, and the exposition of these views lulled many into a 

 feeling of security which they paid for with their lives. The 

 theory of the " pyrophiles " is dangerous to humanity. 



The Revue Scientifique of September 13 contains a report by 

 the delegates of the Paris Academie des Sciences on the eruption 

 in Martinique of May 8. 



This first refers to a chronological account of the eruptions 

 and various volcanic manifestations before the destruction of 

 St. Pierre, and gives a description of the crater of Mont Pelee. By 

 the eruption many fissures were formed, the existence of which 

 is recognised by lines of steam vents. These continued beneath 

 the sea, and accounted, no doubt, for the interruption of the 

 cables and the numbers of dead fish observed on May 5. From 

 these fumaroles steam and sulphuretted hydrogen escape, and 

 round their orifices crystals of sulphur and sal-ammoniac are 

 found. Their temperature at a depth of 010m. is about 

 400 C. Along the beds of the rivers Blanche and Seche, and 

 particularly near their mouths, these vents are very vigorous, 

 but they vary in their activity and give rise to variations in the 

 temperature of the water in the rivers. 



The cinders which fell at Precheur formed a layer about 

 25 centimetres in thickness. At Carbet lapilli one centimetre in 

 diameter were common. Some fragments were larger, and were 



