July 24, 19 19] 



NATURE 



407 



requirements and the structural arrangements of 

 the ships. Provision is now generally made for 

 three operators, namely, the rangetaker, who also 

 controls the rangefinder in elevation ; the trainer, 

 who is provided with a sp)ecial sighting periscope ; 

 and the scale reader, who transmits the ranges to 

 the fire control station. 



The advent of aerial craft has necessitated the 

 use of special combined range and height finders 

 which automatically determine the height of the 

 target from its range and elevation. In the case 

 of naval anti-aircraft instruments, the vertical 

 from which the elevation is reckoned is defined 

 by means of a damped pendulum device. Anti- 

 aircraft height finders for land purposes have the 

 advantage of a steady platform, and in some 

 respects the problem is simpler, as the horizontal 

 can then be determined with sufficient accuracy 

 by means of a good spirit level provided upon the 

 mounting. 



\\'hereas the range of an approaching aero- 

 plane changes so rapidly as to make the operation 

 of maintaining the coincidence of the partial 

 images in the field of view of a rangefinder a 

 matter of some difficulty, the height of the aero- 

 plane remains comparatively constant for consider- 

 able periods. It is generally more convenient, 

 therefore, to measure the height, from which the 

 setting of the gun can be readily adjusted in rela- 

 tion to a suitably engraved gunsight scale. As the 

 range is a function of the elevation when the 

 height is constant, an arrangement has been de- 

 vised whereby the partial images of the moving 

 aerial target are kept in coincidence by the simple 

 operation of following the target. For this pur- 

 pose, the elevating gear is arranged to act upon 

 the deflecting prism of the rangefinder through the 

 intermediary of conical spiral g^ars, which are 

 equivalent to cams of the requisite form. If the 

 height alters, the partial images can be brought 

 again into coincidence by independent direct 

 operation of the working head. Both heights and 

 ranges are indicated by the instrument, the latter 

 being better suited to gunnery purposes when the 

 aircraft appears at a long distance over the 

 horizon. 



The problem of hitting enemy aircraft at long 

 ranges is greatly complicated by the necessity of 

 taking account not only of the interval that must 

 elapse between the finding of the range (or height) 

 and the setting of this upon the gun-sights and the 

 laying of the guns, but also of the greater 

 interval between the time of firing of the gun and 

 the arrival of the shot at its destination. The gun 

 has to be sighted and laid, not for the ascertained 

 position of the target, but for the position that it 

 may be expected to occupy after an interval, it 

 may be of thirty seconds or more, during which 

 time the target may have travelled 1000 or even 

 2000 yards from the position that had been deter- 

 mined. The new and difficult problems thereby 

 involved have already been solved, more or less 

 completely, by the invention of predicting instru- 

 ments closely associated with the range and height 

 finders. James Weir French. 



NO. 2595, VOL. 103] 



THE BOURNEMOUTH MEETING OF THE 

 BRITISH ASSOCIATION. 



THE eighty-seventh meeting of the British 

 Association for the Advancement of Science 

 will this year be held at Bournemouth, under the 

 presidency of the Hon. Sir Charles A. Parsons, 

 K.C.B., F.R.S., on September 9-13. The last 

 meeting was held at Newcastle-upon-Tyne in 1916, 

 the 1917 and 1918 assembUes having been aban- 

 doned owing to obstacles brought about by the 

 war. This was the first break in the annual meet- 

 ings of the Association since its inception in 1831. 

 With the return of peace and happier conditions, 

 it is anticipated that the Bournemouth meeting 

 will be a successful and memorable one. 



A strong local executive committee, with the 

 Mayor as chairman, has been energetically at 

 work for some months. The preliminary arrange- 

 ments are well advanced, and every effort is being 

 made to ensure the complete success of the meet- 

 ing. So far as organisation is concerned, nothing 

 is likely to be lacking, and it only remains for 

 those interested or engaged in scientific work to 

 take full advantage of the opportunities offered to 

 them. Already the number of applications for 

 election as annual members and associates is con- 

 siderable, and doubtless as the date of the meeting' 

 approaches it will increase rapidly. 



The Association will find a home in the 

 Municipal College, a fine building, centrally situ- 

 ated, which was erected shortly before the war. 

 Practically the whole of the college rooms will be 

 placed at the disposal of the Association for the 

 week, and will afford ample and conveniently 

 centralised accommodation for its many and 

 varied activities. Only the large public assemblies 

 — the inaugural general meeting, at which the 

 president's address is delivered ; the discourses by 

 Sir Arthur Evans, F.R.S., and Mr. Sidney G. 

 Brown, F.R.S. ; and the usual conversazione — 

 will be held elsewhere. The Winter Gardens 

 Pavilion, which is capable of seating an audience 

 of upwards of 1200, will be the scene of these 

 functions. 



The programme of work is very full, and the 

 week will be one of great activity. For the seri- 

 ous worker there will, as always, be many in- 

 teresting papers and discussions, while the 

 rumour that hitherto carefully gnjarded secrets of 

 the work of men of science in the war will be 

 made known for the first time is sufficient to 

 appeal to the imagination of the general public 

 and to focus attention upon the meeting. 



Social functions will not form a marked feature 

 of this meeting. The on'ly official entertainment 

 on a large scale will be the conversazione at the 

 Winter Gardens on September 10. But Bourne- 

 mouth is widely famous for its manifold attrac- 

 tions, and members and associates will have no 

 difficulty in finding numberless opportunities for 

 relaxation and amusement in their leisure hours. 



In a popular seaside resort in September the 

 pressure on the available accommodation will 

 probably be great. Those attending the meeting 



