DISCOVERY 



99 



required twelve to learn it when they ran in it \\ ith a 

 two-day interval. 



A third group of facts which has been established with 

 regard to learning by heart concerns the most economical 

 division of the material. If a group of people were 

 asked to learn a poem by heart, practically all of them 

 would repeat each verse over and over until it was 

 known before going on to the next. Does the univer- 

 sality of this method rest on its superiority ? Experi- 

 mental evidence shows that it does not. The most 

 economical method is to repeat the poem as a whole, or, 

 if very long, to divide it into the largest sections that 

 can be grasped as wholes. The size of these will vary 

 with the e.xperience and intelligence of the learner. 

 If the material to be learned is very difficult and 

 unfamiliar, it may be better to learn it in short sections. 

 It appears also that sectional learning is better for 

 motor activities such as complicated drill movements. 

 Recent experiments have shown that rats learn a maze 

 more quickly by learning it a part at a time, and that 

 human beings resemble them in this when they learn 

 maze paths under experimental conditions. 



Another aspect of human learning is that the acquire- 

 ment of one habit usually makes it easier to acquire 

 another similar to it. Thus each piece of music is, 

 on the whole, learned more easily than the last. The 

 habits formed in one piece do not interfere with the 

 habits necessary for another. In this, again, the rat 

 resembles man. He learns each successive maze with 

 greater case, and attacks his later problems \\dth the 

 confidence and apparent enjojinent of his performance 

 which characterise the work of a skilled musician. 



Judging from the evidence at hand, there is an 

 extraordinary resemblance between the laws of animal 

 and human learning when the task concerned is the 

 acquisition of motor habits. The inquiry into the 

 subject of the differentiation of human from animal 

 learning on levels higher than that of the acquisition 

 of motor habit offers a fascinating field for research. 

 While a great deal has been written upon the subject, 

 there has been comparatively little exact experimental 

 work. 



Great Britain in the Latest Age. From Laisser Faire 

 to State Control. By A. S. Turbervii.le, M.A., 

 and F. A. HowE, B.Sc. (John Murray, 7s. Gd.) 



Measure Your Mind. By Fk.\nk P. Stockbridge 

 and M. R. Tr.a.bue. (Harrap & Co., los. 6d. net.) 

 A book on Mental Tests by two Americans. See 

 review, p. 106. 



The Islanders of the Pacific, or The Children of the 

 Sun. By Lieut. -Col. T. R. St. Johnston, late 

 District Commissioner of the Lau Islands, Fiji. 

 (T. Fisher Unwin, 25s.) 



An Up-to-date Meteoro- 

 logical Equipment — II 



By Donald W. Horner, F.R.A.S., 

 F.R.Met.Soc. 



Self-recording R.\in-g.\uges 



It is a curious fact that the first rain-gauge to be 

 constructed was not an ordinary instrument but a 

 self-recording one, the principle of which was suggested 

 by Dr. (afterwards Sir Christopher) Wren, who is 

 better known popularly by his architectural work 

 than by his scientific experiments. On January 22, 

 1662, he demonstrated this particular experiment 

 before the Royal Society by filling a vessel with water, 

 which emptied itself when tilled to a certain height. 

 Ten years later a self-recording rain-gauge on this plan 

 was constructed to the order of the Royal Society.' 



In the first ordinary rain-gauge that w-as constructed 

 the water was not measured but weighed. This 

 pluviometer was invented by Mr. Robert Hooke in 

 1695. 



This rain-gauge was of a very primitive design, 

 merely consisting of a large glass bottle holding more 

 than two gallons and having a neck 20 inches long. 

 The funnel too was made of glass, and was 11-4 inches 

 in diameter, the whole being fixed in a wooden stand, 

 something like an old-fashioned jelly-stand. The 

 funnel was steadied by two pack-threads attached to 

 the frame by pins and passing over the edge of the 

 funnel. The amount of water collected was carefully 

 weighed every Monday morning, and it was found 

 that between August 12, 1695, and the same date in 

 1696, using troy weight, the rainfall in the interval 

 weighed 131 lb. 7 oz. 113 grs., equivalent to 29-11 

 inches. 



This digression into the history of the rain-gauge 

 has been made to show what a very considerable 

 advance has been brought about since the early days 

 of rainfall recording. Primitive simplicity has given 

 way to the complicated mechanism of the up-to-date 

 instruments about to be described. 



In British Rainfall for 1905 Dr. H. R. Mill, the 

 Director at that time of the British Rainfall Organisa- 

 tion, said: "Rainfall duration has not yet been 

 much investigated, and it would be of real importance 

 to obtain additional records on which to base an opinion 

 as to the geographical distribution of rainfall duration." 



To meet this requirement Messrs. Negretti and 



1 " Contribution to the History of Rain-gauges," by G. J. 

 Symons, F.R.S., Quarterly Journal, R.Met. Soc, vol. xvii, 

 No. 79. 



