November 12, 1891] 



NATURE 



ig 



those institutes which make much of athleticism and such 

 matters attract the largest proportion of students, the attend- 

 ance /r^ raid in the class-rooms would not favourably compare 

 with an institute carrying out a purely educational programme." 

 A Polytechnic is mentioned in which, though only seven 

 students entered the class, "scores of young men could be found 

 in the billiard-room and gymnasium " ; and the opinion is ex- 

 pressed that even the excellent work of the Regent Street 

 Polytechnic " would be still better if it could be relieved of the 

 recreative element." 



May I say a word for recreation, as the representative of a 

 College which will eventually form part of the South London 

 Polytechnic, and which has not been " started by a teacher," 

 but has grown up out of a purely recreative institution, for the 

 Victoria Hall (the parent of the Morley Memorial College) is 

 nothing more, unless we use the word in a very narrow sense. 



It is a commonplace truth that the aim of education should be 

 to develop the whole man, not to make mere intellectual experts 

 any more than mere manual experts. Surely recreation has not 

 only a legitimate but a very important place in this, especially 

 where sedentary workers are concerned. Those whose tastes 

 are naturally studious may with comparative safety be left to 

 take)care of themselves. In these days, instruction of some sort 

 may be had by most of those who set their minds on it, and if 

 they miss much which books or the living teacher would have 

 enabled them to gain, at least their energy is not likely to be 

 turned into hurtful channels. Those who desire recreation can 

 also get it, and with little exertion ; but of what kind ? If the 

 gymnasium spoken of above had not been open, what would its 

 scores of frequenters have been doing ? Some, no doubt, might 

 have been in class, improving their minds more than they are 

 likely to do in a gymnasium ; but others, whose youthful spirits 

 need an outlet, would not have been much attracted by study 

 not associated with recreation. The music-hall, or some of the 

 many forms of betting now prevalent, would have been more 

 likely to entice them. In the confined life of our towns it is no 

 small good to provide athletic sports (apart from temptation to 

 drink) as a safety-valve for boyish spirits, even if the good stops 

 short there. But it need not stop short. Of course, there is 

 danger lest the recreative side of an institute or Polytechnic 

 should swamp the educational, unless care is taken to prevent it. 

 A very simple rule, however, issulBcient for this. Our members 

 are not allowed to use the gymnasium or recreation rooms unless 

 they are do/id fide students of at least one class. It is not 

 sufficient that they should take a ticket for a class. The 

 registers are occasionally looked over, and if frequent absence 

 from class is combined « ith frequent attendance in the gymnasium 

 or recreation rooms, a warning, suspension, or even expulsion, is 

 the consequence. We have found that only in an insignificant 

 number of cases is it necessary to proceed to the last resort. 

 Our students as a rule receive an excellent character for steady 

 work from such of our teachers as are in a position to compare 

 them with other students. "I am tired of teaching lads who 

 are trying not to learn," said one who held an important position 

 in a large educational establishment; "your fellows mean 

 business ; it's a pleasure to teach them." And the testimony of 

 others is to the same effect. 



If the moving spirits of a Polytechnic love work themselves, 

 and if they are careful to enlist the sympathy of students, so as 

 to lead them by example rather than drive them by rigid rule, 

 then there is little danger of the institution degenerating into a 

 mere place of amusement. Emma Cons. 



Samuel Morley Memorial College, Waterloo Road, S.E., 

 October i6. 



"W = M,^.'' 



I SHOULD like to take exception to Prof. Greenhill's statement 

 in your issue of September 24 (vol. xliv. p. 493) that " when 

 goods are sold in commerce by weight, they are weighed in 

 scales, and the weight is the same wherever the weighing is 

 carried out, whether at the equator, or the poles, or in \he 

 Moon, Sun, or Jupiter." In this country it is the commonest 

 thing in the world to see goods sold in commerce weighed in a 

 spring-balance, which is also the universal kitchen weighing 

 apparatus, and I respectfully submit that the weight indicated 

 would not be quite the same in the Moon, Sun, or Jupiter, 



The appeal to the scales seems to me to be an attempt to 

 throw dust in our eyes, as what Prof. Greenhill really means is 

 that two equal weights are equal (not each the sxini) wherever 



the weighing is carried on— a balance telling us nothing about 

 the weight, or pull downwards, of either one. 



I was fortunate in getting some of my first notions of dynamical 

 measurements from Thomson and Tait, and hence the appearance 

 of the "blooming g" did not seem unnatural, for after I had 

 learned how to measure a force properly in dynamical units, I 

 was told that a pound's weight = g poundals, or a gram's weight 

 = g dynes, which suffices for reduction to non-absolute units. 

 This, in my opinion, is virtually the same as Prof. Slate's sugges- 

 tion. I never could see why g should appear in dynamical 

 formulas : measure in absolute units, and at the end reduce to 

 pounds' weight from poundals as above. Of course this involves 

 knowing what an absolute dynamical unit is, and it strikes me 

 that a few more "horizontal " experiments with spring-balances, 

 graduated in poundals or dynes, and a little less thinking about 

 arm balances, would go far to clear up difficulties in the minds 

 of students. Arthur G. Webster. 



Clark University, Worcester, Mass., October 14. 



[It will be interesting to see if Mr. Webster can devise a 

 horizontal spring dynamometer which will record within 10 

 per cent, of the true value ; also to know what corrections he 

 would apply for the inertia, teaiperature, and fatigue of the 

 spring, and how he would occasionally test the indications. 

 These difficulties have to be met in Diagrams given by Steam- 

 Engine Indicators. How does the Inspector of Weights and 

 Measures test Spring- Balances in America?— A. G. G.] 



Alum Solution. 

 Perhaps the following evidence of the /rrri-//Va/ superiority 

 of potash alum solution to distilled water in adiathermancy, 

 when the electric arc is the radiant and the "radiometer" a 

 Crookes, may be of interest. The same glass-sided cell was 

 used throughout, and the diffijrence of voltage between the car- 

 bons ("Apostle") was kept sensibly constant (40 volts) through 

 the experiments. Between each observation on the liquids the 

 radiation from the arc was observed unimpeded, save by the 

 glass of the radiometer, as recorded below. The time was 

 given by a metronome (previously examined for constancy) 

 beating half-seconds. No lens was used. 



The current throughout was 6*4 amperes, thickness of each 

 glass plate i'5 mm., thickness of solution 50 mm., distance of 

 radiometer from arc i metre. T. C. Porter. 



Eton College, October 29. 



The Salt Lake of Aalia Paakai. 



I HAVE recently made an analysis of the water of the salt 

 lake of Aalia Paakai, near Honolulu, and have thought that the 

 results might be of interest to the readers of Nature. The 

 lake occupies the crater of an immense tufa cone, whose ejecta 

 cover several square miles, and are especially remarkable for 

 containing numerous aggregations of crystalline grains of pure 

 olivine. The lake is just at mean sea-level, and is scarcely a 

 mile distant from the ocean, but there is evidently no Iree 

 communication with the waters of the sea. 



During the dry months crusts of salt are deposited, sometimes 

 six inches or more in thickness, on the bottom of the lake, and 

 the salt has at times been taken out for use. In the rainy season 

 the salt is wholly redissol ved. The crust of salt is at the present 



NO. II 50, VOL. 45] 



