624 



NATURE 



[October 17, 1907 



Lambayeque. Lastly, in Boletin No. 54 Mr. G. Klingc 

 gives the mineral statistics of Peru for the year 1906. 

 The production included 79,969 tons of coal, 70,832 tons of 

 petroleum, 20,226 tons of salt, 2598 tons of borates, 1830 

 tons of sulphur, 230 tons of silver, 13,474 tons of copper, 

 2568 tons of lead, 2304 kilograms of mercury, and 1247 

 kilograms of gold. 



M. A. Pelletan, in the October number of the Journal 

 de Physique, expresses his regret that in France there is 

 so much difficulty in finding persons capable of determin- 

 ing the elements of an optical instrument by any of the 

 modern methods. It seems singular that in a country 

 through which a knowledge of mathematics is more 

 widely spread than elsewhere, that knowledge should find 

 fewer practical applications than it does in almost any 

 other country. M. Pelletan suggests the formation of a 

 Government office to which engineers whose knowledge or 

 leisure would not allow them to cope with mathematical 

 difficulties might bring their problems for solution. In the 

 meantime, he gives a clear risumi of the general methods 

 of treating geometrical optics which have been developed 

 from Hamilton's characteristic function. These methods 

 are not so well known in this country as they deserve to 

 be, and we have not yet risen to the point of regretting 

 our want of knowledge of them. 



The measurement of the angle between the optical axes 

 of a biaxial crystal has always played an important part 

 in the identification of the crystal, and several -methods of 

 making the measurement are in common use. There has, 

 however, been little comparative or critical study of the 

 accuracy of the different methods under different conditions. 

 A considerable portion of the American Journal of Scierice 

 for October is devoted to such a study from the pen of 

 Mr. F. E. Wright, of the Carnegie Institution. During 

 the course of his experimental work, Mr.' Wright has 

 constructed a double-screw micrometer ocular with the 

 screws at right angles to each other which he uses to 

 determine the position of any point on the interference 

 figure produced when a thin plate of the crystal is 

 examined in plane polarised convergent light. By this 

 means he is able to obtain more accurate results than 

 were possible with the ordinary micrometer in Becke's 

 method. He advocates the use of the stereographic pro- 

 jection in preference to any other. 



An interesting account. of the processes recently devised 

 for liquefying air on an industrial scale, and for e.xtract- 

 ing o.\ygen directly, from the liquefied product, is con- 

 tained in an article by Prof. E. Mathias in the Revue 

 generale des Sciences (No. 17, p. 697). Particular 

 attention is directed to . the method of liquefaction 

 developed by Claude, in which the principle of expansion 

 with the performance of external work has been adopted 

 with remarkable success. The process patented by Thrupp 

 in 1898, and that described by Linde in 1901, are also 

 described^ The problem of separating air into its con- 

 stituents oxygen and nitrogen, which has formed during 

 the past few years so prominent a goal for the endeavours 

 of engineers of all countries, is dealt with at somewhat 

 greater length, the many schemes suggested being con- 

 sidered in detail. Such success has attended the efforts 

 made to separate the gases of the air industrially by 

 liquefaction that the expenditure involved in preparing 

 I kilo, of pure nitrogen on the large scale has fallen 

 below a penny. The article is illustrated by nineteen 

 drawings showing the principle of the various types of 

 plant in use. 



NO. I 98 I, VOL. 76] 



.\ SEVENTH and enlarged edition of the translation by 

 H.R.H. Princess Christian of Prof. Friedrich Esmarch's 

 " First Aid to the Injured," with additional illustrations, 

 has been published by Messrs. Smith, Elder and Co., at 

 2s. net. 



Ne.\rlv half of the thirteenth edition of Mr. VV. H. 

 Harling's illustrated catalogue of mathematical drawing 

 instruments is new matter. Every requirement of the 

 architect, draughtsman, and student appears to be antici- 

 pated. The needs of teachers of practical mathematics 

 have been borne in mind, and considerable space is given 

 in the additional pages to particulars concerning instru- 

 ments for measuring with precision lengths, angles, and 

 other dimensions. 



Mr. H. K. Lewis has published a third edition of 

 "Hygiene and Public Health," by Dr. Louis C. Parkes 

 and Prof. Henry R. Kenwood. The present work grew 

 out of Dr. Parkes's " Hygiene, or Public Health," which 

 appeared in 1899, and was reviewed in Nature of January 

 30, 1890 (vol. xli., p. 290). A certain amount of new 

 matter has been introduced into the present edition, but 

 some parts of the previous issue have been compressed 

 and abbreviated. The size of the page, too, has been 

 slightly enlarged. 



A FIFTH edition of the late Prof. P. G. Tail's well- 

 known " Properties of Matter " has been published by 

 Messrs. A. and C. Black at ys. 6d. The work appeared 

 first in .April, 1885, and was reviewed at length in our 

 issue of August 6, 1885 (vol. xxxii., p. 314), by Lord 

 Rayleigh. The present edition has been edited by Prof. 

 W. Peddie, of the University College, Dundee. The recent 

 advance of physical science has necessitated some additions, 

 but these have in every case been placed within brackets 

 and initialed by the editor, so that the original plan of 

 the book has been preserved. 



pUR ASTRONOMICAL COLUMN. 



A New Comet. — A telegram from the Kiel Centralstelle 

 announces the discovery of a new comet by Mr. Mellish on 

 October 13. Its position at i6h. om. (Madison-Wisconsin 

 M.T.) on that date was R.A. =8h. 31m., dec. =9° 24' S., 

 and the comet was moving slowly in a north-westerly 

 direction. 



This position lies between one-quarter and one-third the 

 distance from 1 to C Hydrse, and the comet is apparently 

 travelling towards Canis Minor. At present it rises a 

 little to the south of east at about 2 a.m., and crosses the 

 meridian at 7 a.m. 



Sun-spot Spectra. — .At the June meeting of the Royal 

 .Astronomical Society, Prof. Fowler announced that he had 

 found a terrestrial origin for the numerous short, hazy 

 lines, known as " band " lines, in sun-spot spectra which 

 have hitherto remained unorigined. These lines, it now 

 appears, are part of an extensive " fluting " spectrum 

 ascribed by Liveing and Dewar, in 1881, to a compound 

 of magnesium and hydrogen (Proc. Roy. Soc, vol. xxxii., 

 p. 190), and investigated by Sir Norman Lockyer. 



The brightest fluting begins near \ 5211, and fades off 

 towards the violet ; a second includes the well-known hazy 

 spot lines at XX 516.1-^. 5i6o-i, 5156-8. &-c., whilst others 

 begin at \ 5620 and on the violet side of H0. A com- 

 parison of the laboratory wave-lengths obtained by Prof. 

 Fowler with those observed in the sun-spot spectrum 

 places the identification beyond doubt, and it is estimated 

 that probably several hundreds of the sun-spot " band " 

 lines will be found to agree, in position, with those occur- 

 ring in the laboratory spectrum (Monthly Notices R..-\.S., 

 vol. Ixvii., p. 530, June). 



Q 



