May 15, 191 3] 



NATURE 



279 



such departments as these it is the authors' desire to 

 impress the geographical point of view upon the 

 specialists in other departments of knowledge. The 

 geographical application of the authors' suggestions 

 is not always clear — some of the details instanced in ' 

 connection with fairs may serve as examples — and 

 again, the geographer who attempts to take up such 

 a topic as the "prehuman" condition of a given dis- 

 trict is certainly liable to disappointment at the results 

 obtainable. On these counts the impression may be 

 felt that the writers of this pamphlet have spread their 

 net too widely. They appear (and they are not alone) 

 to forget their own definition of human geography, 

 which has been quoted above. But if this be a fault 

 it is far better than that of taking too narrow a view, 

 and the pamphlet, criticism apart, must be regarded 

 as profoundly suggestive, and as having been worked 

 out with very great care. 



A party of students, under the direction of Prof. 

 K. Honda, made some interesting simultaneous ob- 

 servations at different stations during August, 1912, 

 on the seiches of Lake Inawasiro (Japan). The lake, 

 which is near the well-known volcano Bandai, is 

 about 12 km. long- and 10 km. wide, and has a mean 

 depth of 51 \ metres. The limnimeters show that 

 there were two oscillations of considerable amplitude 

 with mean periods of 19-11 mins. and 8-89 mins., 

 corresponding to the uninodal and binodal oscillations 

 of the lake. A model of the lake was constructed, 

 and the water in it was made to oscillate by means 

 of a vibrating rod. The periods of the oscillations 

 in the model correspond to periods of 19-53 a °d 9 - n 

 minutes in the actual lake, while the forms of the 

 nodal lines were clearly shown by means of aluminium 

 powder with which the surface of the water was 

 dusted. 



A USEFUL method of calculating- the mean variation 

 by tin- aid of a calculating machine is given by Prof. 

 Knight Dunlap in the current number of The Psycho- 

 logical Review. If in a given series of N terms, with 

 average M, P terms be greater and R terms be less 

 than the average, then the mean variation may be 

 calculated from either of the two formulae, 

 SP l'.N R.M-SR 



N or X 



"By the use of the calculating machine, great accu- 

 racy may be obtained with the minimal expenditure 

 af time and energy," if such methods as the above 

 are followed, which dispense with the numerous sub- 

 tractions of the older method. 



From the report of the joint committee appointed 

 the Institution of Electrical Engineers, the Institu- 

 tion of Gas Engineers, the Institution of Municipal 

 ind County Engineers, and the Illuminating 

 Engineering Society, on street lighting, with which 

 Mr. Trotter opened the discussion of the subject at 

 the last meeting of the Illuminating Engineers, and 

 : rom the reports of the discussion which have appeared 

 in the technical Press, it seems possible that the 

 measurement of the minimum illumination of a plane 

 ;<i in. above the ground will eventually be accepted 

 '- the criterion of good or bad lighting of a street. 

 NO. 2272, VOL. 91] 



The classification proposed b\ the committee i^ as 



follows: — Class A, minimum o-oi ; B, 0025, (', .1114: 

 I >, o-6; E, 010 foot-candle. 



When a curve is drawn in the ordinary way In 

 represent the effect of light upon a photographic- 

 plate, the part of it that represents the effect of the 

 shortest exposures is exceptional in that it show-, a 

 gradatian that is less steep than the part that follmv- 

 it, and gradually approximates to it. This excep- 

 tional part was called by Messrs. Hurtcr and Driffield 

 the "period of under-exposure," and plate-makers 

 were advised to reduce it as much as possible, and 

 photographers to avoid it. But this "period" cannot 

 be eliminated, and therefore in practical work it re- 

 mains, as it always has been, of very great importance, 

 although Messrs. Hurtcr and Driffield dismissed ii 

 with but little consideration. After an interval of 

 more than twenty years, Mr. F. F. Renwick, of 

 Ilford, Ltd., has taken up the study of this particular 

 period, and in the April number of the Journal of the 

 Royal Photographic Society there is published a 

 paper upon it that he recently communicated to the 

 society. Mr. Renwick finds that the "under-exposure 

 period " is not so disadvantageous as some theo- 

 reticians have endeavoured to prove it to be, and to a 

 certain extent he justifies the practical workers who 

 utilise it to the utmost. He shows the nature of this 

 part of the density curve in many various plates and 

 printing papers, giving full details, and points out that 

 as the curve in printing papers is of the same general 

 character as that in the negative, the gradation error 

 of the latter is, more or less, compensated in printing. 



To the Revue ginirale des Sciences of March 30 

 M. Ch. Maurain contributes an article on " Les Etudes 

 d'Aerotechnique a l'lnstitut de St. Cyr." The recently 

 founded aeronautical laboratory at St. Cyr differs 

 fundamentally in its methods from that of almost all 

 other existing institutions for aeronautical research, 

 and its apparatus is designed for the purpose of 

 "approaching as closely as possible to the practical 

 conditions of aerial locomotion." By this is meant 

 scientific experimental research on full-scale models 

 at full speeds, and some work of a preliminary char- 

 acter on wing surfaces has already been accomplished. 

 The work is being extended to experiments on large 

 propellers, and provision is being made for the con- 

 struction of a measuring apparatus sufficiently strong 

 to be able to carry a complete aeroplane. The appa- 

 ratus is mostly out in the open, and consists essen- 

 tially of a track more than three-quarters of a mile 

 in length, along which electrically-driven carriages can 

 be run at speeds up to fifty miles per hour. The 

 measuring apparatus is attached to the carriage, and 

 during the eight or ten seconds in which the speed is 

 maintained constant the forces and couples on the 

 model under test are automatically recorded. Con- 

 currently with these experiments, measurements are 

 being obtained on aeroplanes in flight, and on small 

 models held in a current of air. The latter experi- 

 ments on small-scale models are expected to give 

 information as to the conversion factors for scale 

 which mav become important as the science of aviation. 



develops. 



