June 12, 1919] 



NATURE 



291 



planes. Visibility from above when an aeroplane is 

 seen against the ground is best reduced by using on 

 the top of the wings a ver>- dark shade of green for 

 the high lights, and a bluish-black for the shadows. 

 The surfaces when finished should reflect between 

 4 per cent, and 5 per cent, of the incident light. 

 Visibility from below in the daytime is best reduced 

 by the use of translucent fabrics and dopes. By a 

 suitable blue tint an aeroplane can be rendered almost 

 invisible against a clear sky. Visibility at night is 

 best reduced by painting the aeroplane a matt black. 



The Cambridge Scientific Instrument Co. has 

 issued two lists of thermometers suitable for indus- 

 trial use. List No. 114 dei\ls with glass thermometers 

 for steam plant, the chemical trade, jam- and sugar- 

 boiling, bakeries, breweries, cold stores, and the metal 

 industries. The instruments are well protected, and 

 range from —40° to 540° C. List No. 195 deals with 

 distance thermometers required when the tempera- 

 tures at a number of distant points are to be observed 

 or recorded at some central office. They are of the 

 resistance type, and for observation purposes are con- 

 nected by plug switches to a current indicator in 

 series with a small storage cell. The current is 

 rendered independent of the change of electromotive 

 force of the cell by the aid of a test-switch.- For 

 recording the temperatures continuously a thread- 

 recorder is used. With both an indicator and a 

 recorder installed any thermometer may be con- 

 nected to the recorder and give a continuous record, 

 while the other thermometers can, as desired, be con- 

 nected to the indicator. In both lists full details as 

 to construction and use of the instruments are given. 



An article in Engineering for May 30 makes refer- 

 ence to -the Still combined internal-combustion and 

 steam engine which formed the subject of a paper 

 read before the Royal Society of Arts on May 26 by 

 Capt. F. E. D. Acland. This engine is an internal- 

 combustion engine, the cylinder of which is jacketed 

 with hot water at constant temperature. Heat ab- 

 stracted from the combustion cylinder is employed in 

 converting the jacket-water into steam. The jacket is 

 connected to the water-space of a steam boiler, and 

 this water, on its journey to the jacket, passes 

 through a tubular heater, through which the exhaust 

 gases pass. The steam and water leaving the jacket 

 are led to the steam space of the same boiler. The 

 exhaust gases on leaving the tubular heater are 

 taken through a second heater, through which the 

 feed-water is drawn. The steain from the boiler is 

 used in a steam cylinder which forms the under- 

 side of the combustion cylinder. There is but one 

 cylinder, the upper part of which is an internal- 

 combustion cylinder, and the lower part a steam 

 cylinder. The down stroke is an internal-combustion 

 stroke, and the up stroke is a steam stroke. Remark- 

 able economies are claimed. Thus a Still-Diesel 

 engine with compounded steam side had a consump- 

 tion of 0302 lb. of Admiralty shale oil per brake- 

 horse-power over one hour's run. Full test figures 

 were not given in Capt. Acland 's paper, which is 

 somewhat unfortunate in view of the important 

 features of the new engine. Tt is to be hoped that a 

 complete record of engine dimensions and tests will 

 be published in the immediate future. 



The special catalogues of Messrs. H. Sotheran and 

 Co., 140 Strand, W.C.2, are always of interest and 

 value, and the latest one (No. 772), entitled " Biblio- 

 theca Viatica," is no exception. It gives particulars 

 of upwards of nine hundred second-hand works deal- 

 ing with, among other subjects, maps and atlases, 

 road, railway, and hydraulic engineering. There is 

 also a section, necessarilv not very lengthv, on books 

 relating to ballooning and aeronautics. The catalogue 



NO. 2589, VOL. 103] 



contains many items likely to appeal to readers of 

 Nature, and should be seen by them. 



Messrs. Longmans and Co. have nearly ready for 

 publication Dr. J. F. Spencer's "The Metals of the 

 Rare Earths" and a new edition of J. F. Colyer's 

 "Dental Surgery and Pathology." They have also 

 in the press Dr. R. A. Houstoun's "The Elements of 

 Physics" and E. W. Blocksidge's "Ships' Boats: 

 Their Qualities, Construction, Equipment, and 

 Launching Appliances." Messrs. G. G. Harrap and 

 Co., Ltd., are issuing "General Science," by 

 L. Elhuff, and Messrs. Bailliere, Tindall, and Cox 

 promise a " Popular Chemical Dictionary," by C. T. 

 Kingzett. 



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

 offer in their latest catalogue (No. 179) some four 

 hundred books in new condition at substantial reduc- 

 tions on pre-war prices. The list is a general one, 

 but there is a section devoted to books on natural 

 history and other branches of science. In it we notice 

 Prof. J. C. Adams's 'Scientific Papers," 2 vols.; 

 J. G. Hagen's "Atlas Stellarum Variabilium," six 

 series; R. Braithwaite's "The British Moss-Flora," 

 3 vols.; W. C. Hewitson's "Exotic Butterflies," 

 5 vols.; H. Seebohm's "The Turdidae, or Family of 

 Thrushes," edited and completed by R. Bowdler 

 Sharpe, 2 vols. ; Wilson * and Evans's " Aves 

 Hawaiienses," in parts; and sets of " Biologia Cen- 

 trali-Americana." The catalogue is sent free upon 

 application. 



OUR ASTRONOMICAL COLUMN. 



An Interesting Meteor. — A small fireball was seer» 

 on May ig, n.39 G.M.T., by Mr. Denning at Bristol 

 and by Mr. Mattey at Woolwich ; it moved very slowly 

 from a radiant point hitherto unknown in May at about 

 68*^+63°. The Rev. M. Davidson has computed the 

 real path, and finds that the height of the object was 

 from 53 to 32 miles, the length of the observed luminous 

 course 46 miles, and the velocity about 10 miles per 

 second. The theoretical velocity is 14 miles per 

 second, but atmospheric resistance must have greatly 

 impeded the flight of the meteor. Mr. Mattey saw 

 several other meteors during the latter half of May 

 from the same radiant in Camelopardalus. 



The Sun-spot Maximum.— In reporting on the sun- 

 spots observed in the year igi8 Mr. Evershed, director 

 of the Solar Physics Observatory, Kodaik^nal, re- 

 marks that the maximum spot activity of the 

 present cycle took place during the second half 

 of 1917 for both hemispheres. This judgment 

 may be accepted as correct, for though some 

 hesitation has been felt in accepting this early date 

 lest a secondary maximum should occur after a tem- 

 porary decline, as has happened in previous O'cles, 

 these circumstances do not seem likely to occur. The 

 date of the previous maximum has been placed in the 

 early part of the year 1906, though the sun-spot 

 activity of that year was inferior to that of 1905 and 

 of 1007. .'\dop'ting these estimates as correct, the 

 length of the period just ended is slightly above the 

 average. 



The Mount Wilson OBSERVATORY.--The stellar 

 observations in the programme of the institution of 

 which Prof. Hale is director, hitherto railed the Mount 

 Wilson Solar Observatory, California, or sometimes 

 the Solar Obser^'atory of the Carnegie Institution of 

 Washington, have lately been increasing in import- 

 ance. In view of this fact, and of the practical com- 

 pletion of the loo-in. reflector, which will add greatly 

 to the range and number of night observations, it is 

 proposed that the word " Solar " shall be dropped, and 



