November 6, 1919] 



NATURE 



269 



moreover, large stocks were necessarily accumulated 

 by the various Governments to provide for unforeseen 

 contingencies during the progress of hostilities. In 

 some branches of manufacture these stocks represent 

 several years' normal output. Hence the position of 

 the industry as regards the foregoing products is 

 just now a difficult one. For France in particular, 

 unless the industry is to dwindle and vanish, it will 

 be necessary to devise measures for preventing 

 destructive competition by indiscriminate admission of 

 certain chemicals from other countries. The plan 

 adopted by Great Britain, namely, limited importa- 

 tion, to prevent either undue lowering of prices by 

 "dumping" or excessive charges by manufacturers 

 here, is considered by the writer named to be the 

 best for France to follow until something like normal 

 conditions are again reached. 



Hardness is an extremely important quality, but 

 no satisfactory definition of it has yet been given. 

 The geologist has his scale of hardness, and the 

 engineer has his instruments for measuring the 

 elusive quality. The tests employed by the engineer 

 are good in their way, but they do not, as a rule, 

 measure directly what the manufacturer wishes to 

 obtain in the finished article. A manufacturer of 

 cutlery, for example, is not directly interested in the 

 way his steel gives when a steel ball is placed on it 

 and pressed down with considerable force. But, in 

 spite of the lack of direct applicability in the engineer- 

 ing tests, a good deal can be maintained in their 

 favour, for there is doubtless some connection between 

 the mechanical properties desired by the manufacturer 

 and the readings of the sclerometer, as the instrument 

 for measuring hardness is called. The interpretation 

 of the readings may be difficult, and will probably 

 require the acquisition of knowledge allied to that 

 attained by the skilled craftsman; but, notwithstand- 

 ing the difficulties, the regular use of a sclerometer 

 can be productive of nothing but good. The Magnetic 

 Sclerometer which has been put on the market by the 

 Automatic and Electric Furnaces, Ltd., 281-283 Gray's 

 Inn Road, London, VV.C.i, may prove to be extremely 

 useful in connection with a large and important class 

 of material, viz. hard steels. As its action does not 

 depend upon mechanical phenomena, its range is 

 limited, and it cannot be used for non-magnetic sub- 

 stances. A rod of steel is placed in a yoke so as to 

 form a complete magnetic circuit, and magnetised 

 almost to saturation. The rod is then taken out of 

 the yoke and the remanent magnetism, i.e. the mag- 

 netism which remains after the rod has been subjected 

 to the demagnetising action of its own poles, is 

 measured. To make the measurement the rod is 

 placed in a coil connected to a ballistic galvanometer, 

 and the kick of the galvanometer-needle is noted on 

 the rapid removal of the rod from the coil. The 

 throw of the needle, which indicates the amount of 

 magnetic flux still remaining in the rod, mav be 

 taken as the reading of the sclerometer. In spite of 

 its lack of direct applicability so far as hardness, in 

 the ordinary sense of the \vord, is understood, the 

 magnetic sclerometer should prove to be an extremely 

 useful instrument in the hands of the trained re- 

 searcher, 



Messrs. W. Heffer and Sons, Ltd., Cambridge, 

 have just issued a Catalogue (No. 182) of 1670 second- 

 hand books dealing, among other subjects, with 

 archaeology, folk-lore, anthropology and kindred sub- 

 jects, Egyptology, and philosophy ; also with scientific 

 serials. In the latter section we notice a set of the 

 first 102 volumes of Na.tlri:. The list includes the 

 archajological and fine art library of the late Dr. Allen 

 Sturge. A copy can be obtained free upon application. 



NO. 2610, VOL. 104] 



OUR ASTRONOMICAL COLUMN. 

 Comets. — Schaumasse's comet (1911VII., 1919^) 

 was detected on its return by M. Schaumasse at the 

 Nice Observatory on October 29, being of magni- 

 tude 12. The observation indicates October 19 as the 

 approximate date of perihelion. The following 

 ephemeris is for Greenwich midnight (corrected 

 approximately by the above observation) : — 



Log > 



Log :i 



R.A. N. Decl. 



h. m. s. o / 



Nov. 5 ... 12 27 23 6 28 00914 02610 

 9 ... 12 41 25 5 19 00951 02622 

 13 ... 12 ss 13 4 II 0-0993 0-2634 

 17 ... 13 8 47 34 0-1038 0-2649 

 21 ... 13 22 5 I 58 0-1089 0-2666 

 As the distances from both sun and earth are increas- 

 ing, the comet will remain faint. 



Continuation of the ephemeris of comet 1919c for 

 Greenwich midnight : — 



R.A. S. Decl. R.A. S. Decl. 



h. m. s. o , h. m. s. „ , 



Nov. 7 17 o 44 10 30 Nov. 19 17 41 42 16 57 

 II 17 13 56 1241 23 175620 19 o. 



15 172732 1450 27 r8ii28 2059 



The comet is approaching perihelion and growing 

 steadily brighter, but it is too near the sun for con- 

 venient observation. 



The Sources of Stellar Energy. — There have re- 

 cently appeared two articles on this subject by Profs. 

 Russell and Eddington. The first (Publications Ast. 

 Soc. Pacific, August, 1919) points out the apparent 

 inadequacy of the contraction hypothesis to explain 

 the long duration of the output of energy (far in 

 excess of Lord Kelvin's twenty million years) which 

 is suggested by geology and by various other argu- 

 ments. Hence it is concluded that there must be some 

 unknown source of energy in the interior of giant 

 stars, which dies down before the dwarf stage is 

 reached. Making the supposition that the tempera- 

 ture is insufficient for the unknown source to oome 

 into action in the pre-M stage of giant stars, ProL 

 Russell shows that this stage would be short and 

 extremely few stars would be in it at a time ; he thus 

 explains our failure to detect stars in this stage. 



He also points out that the hypothesis would do- 

 away with the difficulty which Prof. Eddington ex- 

 pressed about the maintenance of the pulsations in 

 Cepheid variables, viz. that the leakage of heat'from 

 the hotter to the colder regions would damp out the 

 oscillations in a few thousand years. For the un- 

 know^n source would supply heat to the interior^ at 

 the greatest rate when it was hottest, thus making 

 good the leakage. 



Prof. Eddington (Observatory, October) makes a 

 bold speculation as regards the unknown source of 

 heat. He reminds us that a large proportion of the 

 total energy of a star is locked up in its atoms, so 

 that the energy would not be exhausted when the star 

 cooled. It would need to be annihilated to liberate 

 all the energy. He asks whether this annihilation of 

 matter may not be going on in giant stars: "When 

 a positive and negative' charge collide centrally they 

 go out of existence." He points out that at moderate 

 temperatures the outer electrons of the atom form a 

 protecting cushion ; but, in a very high temperature, 

 ionisation is presumed to take place, robbing the 

 nucleus of its protecting electrons and leaving it an 

 exposed target. He makes an estimate that i atom 

 out of 5x10" must be annihilated each second. At 

 this rate it would take about 2X10" years to annihi- 

 late the whole star, so that the loss of mass in the 

 periods usually assigned to the giant stage would be 

 trifling. 



