3H 



NA TURE 



[Septembkr 9, 1909 



in a most flourishing condition. It lias 650 members and 

 an annual income of more than 100,000 francs, part of 

 which is derived from the Department of Agriculture of 

 the country. The society further possesses about thirty 

 endowments, amounting together to more than a million 

 francs, the income from which it utilises in various ways, 

 as, for example, in prizes to inventors who benefit industry, 

 ir assisting inventors or artisans who have come down in 

 the world, &:c., all calculated to forward the object of 

 the society. In addition, in its monthly bulletin, which 

 is a quarto volume of two hundred pages, it gives its 

 members well written and illustrated articles on industrial 

 questions of the day. In the July number, leaving out of 

 account the shorter articles, there are reports on the 

 breweries and distilleries of the north of France, on recent 

 girder bridge-work, on the position of the electrical in- 

 dustry in France, and, lastly, forty pages of a serial arlicl-; 

 on the economic situation in Great Britain. 



The Engineer for August 27 comments on the reasons 

 for the success of the French in following up new lines 

 of research, and says that it is probably to be found in 

 the fact that they often allow themselves to be influenced 

 by imagination rather than by the practical aspect of the 

 problems they are trying to solve. The remark is called 

 forth by the interest which is being taken on the other 

 side of the Channel in the evolution of the aeroplane, as 

 evidenced by the meeting at Rheims. We agree with our 

 contemporary that, not only the possession of a healthy 

 imagination, but also unbounded enthusiasm, are qualities 

 which go to make a good inventor. Can the fact that 

 this country is taking so small a part in the development 

 of aerial machines be accounted for by the absence of 

 inventive faculties? We prefer to believe that it is rather 

 the lack of financial support which is causing the stagna- 

 tion, a lack which may be explained by the well-known 

 desire of British manufacturers to see commercial success 

 and profit within reach before taking up any industrial 

 development. Given funds, there is no doubt that we have 

 men of ability sufficient to bring this country into line with 

 our neighbours. 



The leading article in Eiigiuecring for -August 27 is 

 devoted to the address of the president of the British 

 Association. Many of the statements in the address are of 

 particular interest to engineers, and one appeals very 

 forcibly. Sir Joseph Thomson quotes Helmholtz as saying 

 that often in the course of a research more thought and 

 energy are spent in reducing a refractory piece of brass to 

 order than in devising the method or in planning the 

 scheme of campaign. This is exactly in accord with 

 engineering practice. For example, in developing a certain 

 steam turbine, the thermodynamic and kinematic questions 

 involved occupied not a tithe of the time and thought 

 which had to be expended on such questions as the mere 

 form of the casing. Should it, for instance, open at a 

 transverse joint or a longitudinal one? Would the 

 governor fit in better at one end or at the other? These 

 and other apparently trivial, but really very important, 

 details absorbed the greater part of the time at the 

 designer's disposal. The mathematician seems often to 

 have a difficulty in appreciating this matter, but the ex- 

 perimental physicist is nearer akin to the engineer, and 

 has to face many of the same problems. Both suffer from 

 a certain apparent perversity in the materials they use, to 

 which, however, the engineer has commonly the added 

 burden of often wayward and intractable human nature. 



Messrs. H. F. Angus and Co., 83 Wigmore Street, 

 .■^ndon, W., have submitted to us a specimen of a very 

 NO. 2080, VOL. 81] 



useful supplementary lens which they have placed on the 

 market for attachment to a naturalist's telescope. The 

 telescope sent with the lens is of the usual short-focus 

 pattern made for observing birds or other objects, and by 

 placing the supplementary lens over the objective the 

 instrument can be used to watch insects or similar small 

 forms of animal life at any convenient distance down to 

 about 20 inches, at which distance the magnification is 

 about five diameters. The combination thus provides the 

 naturalist with a very handy means of studying the 

 characteristics and movements of insects, spiders, and so 

 on at a convenient disla'nce, and without disturbing the 

 creatures. Similar caps can be adapted to the ordinary 

 tourist telescope and the monocular prismatic field-glass. 

 The attachment is inexpensive — the price being 3s. 6d. 

 for any size or power lens required — and it certainly in- 

 creases the optical capacity of any instrument with which 

 it is used. For the observation of minute forms of animal 

 life in the open air, and for the examination of details of 

 objects placed beyond the distance of distinct vision in 

 museums, the additional lens will be found a great 

 advantage. As, however, accessory parts of instruments 

 are often misplaced or not at hand when desired, we 

 suggest that the attachment should be fixed upon the 

 telescope by a band or other means which would permit 

 the lens to be brought in front of the objective or turned 

 away from it as desired. A simple swivel arrangement 

 would probably enable this to be done, and the naturalist 

 could then immediately convert his glass into an instru- 

 ment for the observation of objects near or far. 



OUR ASTRONOMICAL COLUMN. 

 Changes on Mars. — Further changes in the south polar 

 regions of Mars are recorded by M. Jarry Desloges in 

 No. 4350 of the Astronomische Nachrichicn (p. 95, 

 August 25). Observations, made at the observatory in- 

 stalled on the Revard plateau, on .'\ugust 20, iih., showed 

 that the Mare Cimmerium was divided obliquely by a 

 bright band between Eridania and Electris, whilst a large 

 gulf was distinguished on Zephyria, and numerous changes 

 were seen to have taken place on the northern plains. 

 Since its separation, observed on August 11-12, the bright 

 oval region in longitude 320° has become more and more 

 separated, and the dark regions of the planet, so pale in 

 June and July, are changing, and becoming darker, almost 

 daily. A greyish region seen at the eastern side of the polar 

 cap on August 13, ah., is diminishing rapidly, and appar- 

 ently disaggregating in all directions. 



The Absorption of Light in Space. — A suggestion 

 recently made by Prof. Turner, in regard to M. Tikhoff's 

 researches on the absorption of light in interstellar space, 

 is discussed by Mr. J. A. Parkhurst in the July number 

 of the Astrophysical Journal (vol. xxx.. No. i, p. 33). 

 Prof. Turner's suggestion was that photographs of stars 

 should be taken using only the visual rays, and then other 

 photographs should be taken in the same way to deter- 

 mine the increase of exposure necessary to get stars of a 

 definite number of magnitudes fainter. If these photo- 

 graphs were more in accordance with the theoretical law 

 connecting exposure and intensity than are those where 

 the violet rays are not excluded, they would afford 

 evidence that the discoidance between visual and ordinary 

 photographic magnitudes is due rather to cosmical than to 

 photographic causes. Evidence of this nature has already 

 been adduced by M. Tikhoff. 



Mr. Parkhurst shows, however, from a number of ex- 

 periments carried out at the Yerkes Observatory, that his 

 results are contradictory to those of M. Tikhoff, and 

 suggests that the cause of the difference lies in the instru- 

 ments and pLites employed ; probably, in the main, in 

 the plates and light-filters, for the same effect has been 

 obtained by him both with a reflecting telescope and a 

 doublet camera. Thus it would appear that the proposed 



