226 



NA TURE 



[January 9, 1902 



in tlie results is one of fundamental importance. Berson's 

 numbers clearly do not go to the end of the matter, for 

 with a little play of the imagination in the region of 

 extrapolation, his results bring absolute zero within sight 

 at the very moderate height of some thirty miles, 

 whereas -6S^ C. is the lowest temperature recorded in 

 the flight of the unmanned balloon Cirrus froin Berlin, 

 which is reported to have reached a height of 18,000 

 metres. This, by a curious coincidence, is identical with 

 the lowest temperature recorded at the earth's sur 

 face. It was registered at Wercliojansk, in .Siberia, on 

 January 15, 1885 ; a still lower temperature, -70 C, is 

 given in the Meteorologische Zcitscltrifc for June as 

 registered by the apparatus of an unmanned balloon 

 started from Vienna on January 10 of last year. Kite 

 observations also afford information as to the rate of fall 

 of temperature under varied meteorological conditions. 

 But the height which they can attain does not give them 

 a final voice in the determination of the question of the 

 lowest limit of atmospheric temperature. 



Another quantity for the determination of which balloon 

 observations are specially appropriate is the constant of 

 solar radiation, but the results are not yet final and the 

 subject is too wide for this occasion. 



It would be a matter for congratulation if Glaishers 

 exploration of the upper air could be continued by his 

 own countrymen. Investigations have, mdeed, been 

 made recently by the Rev. J. M. Bacon, and, under the 

 auspices of the Aero Club, by the Hon. C. S. Rolls. 

 But for the use of balloons on any considerable scale 

 these islands are not very suitable. It will hardly yet be 

 forgotten that some years ago an attempt to pursue 

 scientific investigation in this manner resulted in the loss 

 of a valuable life. Work with kites even is not without 

 its dangers, but it is satisfactory to note that the Royal 

 Meteorological Society has taken up this mode of inves- 

 tigating the upper atmosphere, and has not only moved 

 the British Association to devote a sum of money for the 

 purpose, but has secured the active interest of the presi- 

 dent of the Society, Mr. \V. H. Dines, in the undertaking. 

 The British Isles occupy such an exceptional position 

 with regard to the passage of weather changes from the 

 Atlantic Ocean that the results of a properly directed 

 inquiry of this character can scarcely fail to throw im- 

 portant light on many meteorological questions. 



One of the results of the Congress of Meteorologists 

 .at Paris in 1900 was an international arrangement for 

 the simultaneous exploration of the upper air in the 

 various countries of Europe by means of unmanned 

 balloons carrying self-recording instruments. An ascent 

 was to be made on a fixed day in the first week of each 

 month. Prof. Hergesell, of Strassburg, chairman of the 

 Aeronautical Committee of the International Conference, 

 undertook the collection and the working out of the 

 results. The ascents have been regularly carried out 

 and brief reports have appeared in the Metci>roloi;isi:hc 

 Zeitscltrift. In this country Mr. V. \. Alexander, of 

 Bath, has carried out ascents of unmanned balloons on 

 some of the appointed days, and has made provision for 

 observations in manned balloons by Mr. Spencer. With 

 the balloon observations are associated observations of 

 ■clouds. We have no system of systematic measurement 

 of cloud movements, but in connection with the balloon 

 Ascents the following observatories have furnished eye 

 observations of the form and motion of clouds on the 

 ■days of the ascents and the preceding and following days, 

 viz. Greenwich, Kew, Oxford, ISidston, ■• Stonyhurst, 

 Rousden, Falmouth, Cllasgow, Aberdeen and Valencia. 

 The returns have been sent to the Meteorological Office 

 to be forwarded to Prof. Hergesell. The details of the 

 ascents of November 8, 1900 (the tenth of the whole 

 series of international ascents) have already been pub- 

 lished, and ihcy show in a very effective manner the 

 initial increase of temperature with height in the region 

 NO. 1680, VOL. 65] 



of the anticyclone which covered the continental 

 stations, Paris, Strassburg, Berlin, Vienna and St. Peters- 

 burg, at which ascents took place. Inversions of tem- 

 perature are also very marked in the discussion of the 

 \ienna observations for the ascent of January 10 by 

 J. \'alentin in the Meteorolof;isdte Zeilsclirift for June. 



For meteorological purposes balloons will be much 

 more serviceable when the means for converting them 

 from aerostats into airships are perfected. It is fifteen 

 years since Commandant Renard, who with his brother 

 has been so active in all that concerns military ballooning 

 in France, published his lecture, " Sur la Navigation 

 Aerienne,'' before the Societe de Secours des Amis des 

 Sciences, in which he lays down with true French clear- 

 ness the dynamical conditions for the airship as dis- 

 tinguished from the aerostat. The publication is 

 illustrated with a picture of an airship corresponding 

 very closely with those of the airship of M. Santos 

 Dumont that have attracted so much public attention 

 within the last few months. At present airships are at 

 best fair-weather vessels, and fair weather is a dull subject 

 for meteorologists. W. N. Shaw. 



GUN-SIGHTS FOR LARGE AND SMALL 

 ORDNANCE. 

 r T P to quite recent times but little has been done by 

 ^ those interested in gunnery to improve in a really 

 practical way the method of aiming either a rifle or gun. 

 The usual method of aiming is much the same as that 

 employed long ago in using the mediaeval crossbow. The 

 object aimed at, the fore- sight and the back-sight, are 

 brought into line by the eye of the marksman, always 

 with this defect, viz., that the eye is out of focus with 

 respect to two of the points mentioned when focussed on 

 the third. We know well that, if we fix our attention 

 on a distant object, our eye will automatically focus itself 

 on that distant object ; and only an indistinct image of 

 the foresight will be present. Again, should we focus 

 the eye on the fore-sight, then the object aimed at will 

 not he clearly seen. This is also true in an accentuated 

 manner with respect to the back-sight, since it is nearer 

 to jthe eye than the fore-sight. The operation of thus 

 aiming, even in the best circumstances of light, is obviously 

 unsatisfactory. 



The gun-sight problem has been attacked by several 

 leading experimentalists, and in the majority of cases 

 some apparatus in which lenses are employed has been 

 used. An early form of optical gun-sight consisted of a 

 small telescope attached to the gun, the telescope being 

 furnished with an eye-piece and cross lines or webs, 

 similar to those used in the surveyor's level or theodolite. 

 This telescope is attached to the rifle by a joint at one 

 end, the other end being raised or depressed to suit the 

 range by means of a milled headed micrometer screw. 

 The telescope-sight has been applied to field and other 

 guns, and to it has been added an inclinometer, so that 

 an angle inclination either above or below the horizontal 

 line can be given to the gun. 



Objections have been raised to the telescope-sight, and 

 it has been urged that the field is limited, so that it is 

 not easy to " pick up" the object to be hit, and that the 

 object appears to be moving with a speed greater than 

 its real one, also that when heavy charges of gunpowder 

 are used, and the recoil is considerable, there is a 

 risk of the eye of the marksman being injured by the cap 

 of the cyc-piece when it is driven back, and also that the 

 adjustment of the telescope may be thrown out, by the 

 concussion on firing the piece. With respect to the first 

 objection, in the case of a man with short sight, the tele- 

 scopesight is of great use since it enables him to see 

 the object as clearly as a man with normal vision. When 

 the telescopic method is used for laying field guns, the 



