28o 



NA TURE 



(July (9, 1900 



stimulus and sensation at ten stages between black and white. 

 A comparison of the last two columns will show the extent of 

 agreement between observation and calculation. The nurnbers 

 given under the head of stimulus are calculated on the basis of 

 the suggested law, the number 27 per cent, of stimulus, as the 

 concomitant of 50 per cent, of sensation, being taken over from 

 observation as a basis for calculation. 



Although I venture to hope that the results of this investiga- 

 tion contribute something towards a solution of the problem, 

 still it will be seen that we have as yet by no means reached the 

 stage at which we can claim that a law expressing the quantita- 

 tive relation of stimulus to sensation is established beyond 

 question. But from the work of many observers we may at 

 least draw the conclusion that there is some well-defined rela- 

 tion, though its law at present eludes the grasp of our 

 generalisation. And this so far lends support to the doctrine 

 of concomitance. 



There has been much discussion as to the true meaning of the 

 relation. Is it primarily a relation between physical stimulus 

 and physiological response, or between physiological response 

 and psychological concomitant ? In other words, is the law we 

 seek primarily a physiological or a psychological law? We 



were only i '22 inch in diameter, and the length of the arms, 

 from the centre of cup to the spindle, only i -96 inch. The 

 author describes at length the whirling apparatus used in making 

 the experiments, and which had been previously used in the 

 year 1888, but in an enclosed space, instead of in the free air. 

 He points out that a whirling apparatus is absolutely necessary 

 for testing anemometers, because we have no other means of 

 accurately measuring the speed of the wind to which the instru- 

 ment is exposed, unless we employ for that purpose some other 

 anemometer, which must .itself be first tested. In the author's 

 view, the effect of using the whirler in the open air is to alter- 

 nately add to and subtract from the artificial wind resulting from 

 the steady motion of the whirler, so that the actual resultant 

 wind afifecting the anemometer acquires a gusty character which 

 is analogous to the conditions always existing in the free air, and 

 the artificial gusty wind thus secured affords a highly appro- 

 priate test-wind for anemometers that are to be used in the 

 open air. The apparatus employed is shown in a plate, which 

 we reproduce. 



The arm, on the extreme end of which the anemometer is 

 placed, is 28 feet long, and is made to rotate either by hand- 

 power or by means of the engine used in the kite experiments. 



Fig. I. —Whirling Machine and Driving Belt for Anemometer Tests. 



cannot enter upon the discussion here. Attention may, how- 

 ever, be drawn to two facts .• — First, that Prof. Pfeffer claims to 

 have shown that the attractive influence of malic acid on the 

 spermatozoids of ferns is approximately in accordance with the 

 Weber- Fechner formula ; and secondly, that Dr. Augustus 

 Waller's researches on the excitation of muscle and nerve indi- 

 cate some such relation, though not exactly this relation, 

 between stimulus and physiological response. In view of these 

 facts it seems not improbable, therefore, that the relation may 

 prove to be primarily physiological. In which case we may 

 infer that sensation is directly proportional to the molecular 

 disturbance in the nerve-centres concerned. 



C. Lloyd Morgan. 



ANEMOMETER TESTS. 

 T^HE U.S. Monthly Weather Review for February contains 

 -*■ an important contribution by Prof. C. F. Marvin on ane- 

 mometer tests. The paper gives the results of a series of 

 experiments to determine the factor of an anemometer spe- 

 cially designed for use with kites at considerable altitudes in 

 the free air. For that purpose the anemometer has necessarily 

 Jo be very small and light, and in the present case the cups 



NO. 1603. VOL. 62] 



By hand-power any speed up to thirty-five miles an hour could 

 be obtained, and by the engine the velocity could be raised to 

 nearly sixty miles an hour. A good break-circuit seconds pen- 

 dulum clock was employed, in conjunction with an astronomical 

 chronograph, to record results, and the series of comparisons 

 appears to have been carried out with much care and com- 

 pleteness. 



The experiments included a redetermination of the constants 

 for a "standard aluminium cup anemometer," in which the cups 

 were 4*07 inches in diameter, and the arms 6'65 inches in length. 

 This instrument had been used in the investigations of 1888, and 

 the values now obtained gave a slightly lower rate of speed of the 

 cups in a given wind than had been formerly deduced. But as 

 the differences did not exceed 2 per cent., it is fair to conclude 

 that, upon the whole, the agreement was satisfactory. 



The author also points out that another result of the experi- 

 ments is to confirm a conclusion arrived at in 1888, viz. that an 

 anemometer with large cups, as compared with the length of the 

 arms, runs at a speed bearing a more nearly constant ratio to that 

 of the wind than an anemometer with relatively larger arms. In 

 the case of the .tsmall kite anemometer now investigated, the 

 factor is practically constant for velocities from ten to fifty 

 miles an hour, the extreme variation being only about i '5 per 

 cent. 



