JtNE lO, 1909] 



NA TURE 



4.^.9 



A NKW nu'thod of illumination for photographic \vorI<, 

 partirulariv for cnlarginij and for proieclion purposes 

 where great magnification is not required, lias been 

 brought under our notice. The apparatus is known as 

 the " Petrolite " photographic lamp, and is sold by Mr. 

 .'\. J. Garrad. of 317 High Holborn, W.C. The lamp 

 consists essentially of an ordinary Welsbach incandescent 

 gas-mantle, which is raised to a condition of incandescence 

 by the use of petrol gas. The petrol is contained in a 

 metal chamber, but is all taken up by a highly absorbent 

 >naterial ; consequently, there is no loose petrol in the 

 container. Once it is absorbed it does not escape, but is 

 only given up again in the form of vapour as it is required 

 at the burner. If from any cause the apparatus is over- 

 turned, the light goes out. The whole appliance will go 

 inside an ordinary lantern body, and is obviously a good 

 arrangement where either ordinary gas or any method 

 of electrical iliumination is unobtainable. The price is 

 reasonable, and the cost of running is lower than that of 

 any other similar method of incandescent gas lighting. 

 1 he apparatus may be commended to those who require 

 a source of light that must be independent of any 

 extraneous supply of gas or electricity. 



\Vk have received from the Bausch and Lonib Optical 

 Co., of 9 Thavies Inn, Holborn Circus, E.C., its latest 

 catalogue of microscopes, apparatus for photomicrography, 

 and various projection appliances. From it we gather that 

 the Bausch and Lonib Co. is now acting in close coopera- 

 tion with Messrs. Carl Zeiss, of Jena, and that many of 

 its products are based on the investigations carried out 

 by the latter firm. The apparatus for photomicrography 

 appears to be now of a very complete order, and is in 

 general design much the same as that made by Messrs. 

 Zeiss, the camera and the portion of the apparatus sup- 

 porting the microscope and optical accessories being re- 

 garded as two separate appliances. While this is what 

 some regard as an objection, the whole apparatus not 

 being fastened to' one single solid base, yet, on the 

 other hand, it ensures that any movement of either com- 

 ponent is not communicated to the other part. The 

 apparatus for the projection of both opaque and trans- 

 parent objects is of new design, and appears to be built 

 in a very substantial way, and is arranged to carry out 

 work of almost any description in this direction As the 

 Bausch and Lomb Co. is now fitting up new showrooms 

 in London, where all these appliances may be seen under 

 working conditions, a visit at the present time cannot 

 fail to be of interest to those who contemplate purchasing 

 such apparatus. 



The Colorado School of Mines Quarterly for April is 

 wholly devoted to a short monograph on tungsten, by 

 H. R. Van Wagcnen. The first part, which is more of 

 local interest, gives an account of the Colorado mines 

 and mill practice. The second part deals with the physical 

 properties and uses of tungsten, its mineralogy, chemistry, 

 and metallurgy. The preparation and properties of the 

 tungsten alloys are also described, and at the conclusion 

 of the paper there is a useful bibliography. The mairt 

 applications of tungsten are found in the preparation of 

 various tungsten steels and of metallic filaments for 

 lamps, other uses being found for tungstates as a mordant 

 in dyeing, in the preparation of non-inflammable fabrics, 

 and as a pigment. 



Attention has been directed more than once to the 

 'growth in size, year by year, of the " Statesman's Year- 

 book," published by Messrs. Macmillan and Co., Ltd., 



NO. 2067, VOL. 80J 



and edited by Dr. J. Scott Keltie with Mr. I. P. A. Ren- 

 wick's assistance. The igog issue, which is now avail- 

 able, represents a successful attempt to reduce the bulk, 

 without affecting the usefulness, of this valuable statistical 

 and historical annual. This satisfactory reduction by some 

 300 pages has been accomplished by the introduction of 

 uniform type, the elimination of superfluities, economies of 

 space, and various re-arrangements. The present issue 

 has several new features; some deal with recent changes 

 in the altered constitutional character of several countries, 

 others with new census returns and various other matters 

 of public interest, while a new section gives a brief state- 

 ment with reference to the Hague Tribunal, with a list 

 of members. The plates, which are all new, include a 

 diagram exhibiting British and German naval expenditure 

 on new construction during the last decade ; and maps 

 illustrating the Anglo-Siamese Treaty, 1909; the Anglo- 

 Abyssinian Boundary, 1902 and 1907; the Anglo-German 

 and German-French Kamerun Boundary, 1906 and 1908; 

 the All Red Route ; and the military divisions of India. 

 The price of the year-book remains 105. bi. net. 



Erratum.— Mr. Hy. Harries informs us that on p. 405 

 of N.nuuE of June 3 the ship on which Dr. von Neumayer 

 returned from Melbourne in iSb4 was erroneously given 

 by him as the So'ccrcign oj the Seas ; it should have been 

 the Garrauiald. 



OUR ASTRONOMICAL COLUMN. 

 The Rings of Saturn.— Prof. Levi-Civito has written 

 an interesting pamphlet on the mechanics of the ring of 

 Saturn C" Sulla Forma dell' Anello di Saturno," Premiale 

 Officine Grafiche Carlo Ferrari, Venezia). His conclusion 

 is that under certain hypotheses the angular velocity of 

 each ring exceeds that of a satellite at the same distance. 

 He points out that the differential equations applicable ta 

 a flexible substance are applicable, even in spite of Clerk 

 Maxwell's demonstration that the ring consists of discreet 

 particles. He therefore reverses the procedure of Stazio 

 in Dante ; — ^^ 



'■ Trattando 1 'ombre come cosa salda. 



Changes in the Figure and Dimensions of the Sun.— 

 In a mathematical paper appearing in No. 4, vol. xxix., 

 of the Astrophysical Journal tp. 257, May), Prof. Mouhon 

 discusses the possibility of observing changes in the form 

 and dimensions of the sun from the dynamical point of 



view. J • 1 



After reviewing briefly the practical methods previously 

 employed to detect any possible variation, he attacks the 

 problem from various theoretical standpoints, with reason- 

 able assumptions, and arrives at several interesting con- 

 clusions. First, he shows that the difference between the 

 equatorial and polar diameters must be less than 007 

 as seen from the earth, and is, therefore, beyond observa- 

 tion by any means yet employed. Then, considermg 

 possible oscillations, he'demonstrates that, if they exist in 

 the sun, their period cannot exceed a few hours,^^ although, 

 different periods might combine to form " beats." 



It seems possible, at first glance, that any possible 

 shrinking might be demonstrated by the change in the 

 rate of rotation before becoming directly measurable from 

 the earth, but Prof. Moulton shows that this is unlikely. 

 Variations of diameter would presumably produce corre- 

 sponding variations of temperature, but it is surprising 

 to find that a variation of the apparent diameter by o-i 

 should produce a change of 1400° C. in the temperature. 

 Considering the effect of such dilatational oscillations on 

 the power of radiation, it is shown that, were the diameter 

 undergoing changes amounting to 01", as seen from the 

 earth, the rate of radiation at maximum would be 2-56 

 times that at minimum radius; in other words, the varia- 

 tion would be about one stellar magnitude. Langley and 

 Abbot believed they had observational evidence of a 10 per 

 cent, variation in the radiation, but this would correspond 



