May 6, 1909] 



NATURE 



277 



4000 miles from the earlli's centre, would just balance 

 the earth's attraction of gravity. So thar, if this attrac- 

 tion were absent, and the two bodies were connected by a 

 rod, or material bond, instead, there would be continual 

 strain on such bond equal to the moon's weight at the 

 eartli's surface. 



Now, the volume of the earth is Sooo'x 05236 cubic 

 miles, or about 4X10-- cubic feet, which, multiplied by 

 52 and 62.2, gives 1375x10-- lb., or 6875x10" tons (the 

 value given by Cavendish's experiment is 6-14X10-' tons, 

 the difference being due to the larger value of the earth's 

 diameter here used), the moon's weight at the earth's 

 surface being, therefore, 6875 -=-80, or 86x10" tons, which 

 would be the strain on the material bond connecting the 

 two bodies as above in the absence of gravity. As 

 this strain varies directly as the mass of the revolving 

 body and the square of its velocity, and inversely as its 

 distance or radius of revolution, then at the moon's actual 

 distance of 240,000 miles, and velocity of 0-64 mile per 

 second, the strain would be diminished by the factors 

 4000 '240000 X (0-64 '5)- or 1/3600; that is, to 86xio"/36oo, 

 or 24x10'^ tons. Thus if some Titan should, like a stone 

 in a sling, whirl the moon at its present velocity and 

 distance around his finger, the strain upon the string 

 would be 24X10'^ tons, which, if the string be of the 

 same thickness as the moon itself, gives about i-6 tons 

 per square inch, necessitating a steel rod about 400 miles 

 in thickness of thirty tons per square inch tenacity, just as 

 Sir O. Lodge states. 



But have we not neglected a very important factor in 

 this computation? As the moon moved away from the 

 earth's surface to its present distance, we allowed for its 

 change of velocity and distance as affecting its centrifugal 

 force ; but should we not also allow for the diminution 

 of gravity at the increased distance? The tension of the 

 stone in the sling upon its restraining cord would be less 

 at the greater distance owing to the decreased velocity 

 and to the effect of the increased distance upon the 

 centrifugal force ; but as the stone moved outwards it 

 would also come into a weaker field of gravltative force, 

 which would further reduce the strain inversely as the 

 square ol the distance (just as if its mass had been 

 diminished), or by the factor 1/3600, thus reducing the 

 total strain of 24X10" tons obtained above for the moon 

 at its present distance and velocity to 24Xio"/36oo, or 

 hjXio" tons for its actual present value, requiring a 

 steel rod only about 61 miles thick and of the same tenacity 

 as before. 



Evan McLennan. 



Corvallis, Oregon, U.S.A. 



The Inheritance of Acquired Character. 



1 HAVE received the following from my brother, Dr. 

 .\. \V. Smyth, late superintendent of the United States 

 Mint at New Orleans. He has experimented with bees 

 and written papers on them, which have been published in 

 several bee-journals throughout the world. 



He says. The commonly accepted view, stated by Dr. 

 Francis Darwin in his presidential address, that the queen 

 bee is entirely isolated, so as to bar the ordinary course 

 of inheritance, is not so. According to Dr. Smyth, some 

 of the workers occasionally lay eggs, and these eggs 

 always produce drones, which, coming to fertilise the 

 queen, opens the path for the ordinary course of inherit- 

 ance. Upon this principle he bases an explanation of 

 the following facts. In Morocco the honey-bee has foes 

 in the form of certain beetles. To guard their stores the 

 bees have come to build pillars of wax at the entrance 

 to the hive, which prevents the entrance of the beetle. 

 This becomes a habit, and a habit that could onlv have 

 arisen as an acquired character, and it could only have 

 reached workers through the queen being fertilised bv 

 drone-offspring of the workers. When a iVIorocco queen 

 is brought to this country, where these beetles do not 

 exist, the progeny of the queen continue to build pillars 

 of wax; in the course of time this acquired habit becomes 

 attenuated. Wm. Woods Smyth. 



Maidstone, April 17. 



NO. 2062, VOL. So] 



THE IMPERIAL SIDE OF THE FUEL 

 QUESTION. 

 "T^HE returns issued by the Board of Trade on 

 ■'■ February 24, dealing with the output of coal in 

 the United Kingdom during 1907, should go far to 

 convince the most callous that our fuel supply is at 

 the present moment every whit as important an 

 Imperial question as keeping up our first line of 

 defence to the two-Power standard or forming an 

 efficient citizen army, and that unless due prominence 

 and consideration is given to it, it is impossible for 

 our Navy and Army, no matter how good, to save 

 the nation for more than a limited period. 



Our kingdom has but two capital assets, labour 

 and coal, and without the latter labour would count 

 for but little in face of competition with nations pos- 

 sessing the means of economic power production ; so 

 that the real measure of England's power and 

 prosperity is to be foimd in her store of unwon coal 

 and her ability to husband the resources with which 

 nature has endowed her in order that she shall retain 

 the same relative position towards other nations that 

 she does at present. 



Not only has America the largest store of coal in 

 the world, but until lately the amount that has been 

 mined has been comparatively small, and out of all 

 proportion to the magnitude of her coalfields. The 

 close of the last century, however, saw her an easy 

 first as regards the output of coal, and she now raises 

 at least a third more than the United Kingdom. 



It is, however, with the position ol nations nearer 

 home in respect to this question that we are at the 

 present time more deeply interested, and in order to 

 gain an idea of the relative life of their fuel supplies 

 as compared witii our own, it is necessary to contrast 

 their rate of output with the available quantities of 

 coal still unused. 



The Royal Commission on Coal Supplies, which 

 sat from 1901 to 1905, collected all the evidence pos- 

 sible as to the amount of coal still existing in this 

 country, which at the rate of output then obtaining 

 would last something like six hundred years, but they 

 also gave warning that " vast as are the available 

 resources, it must be borne in mind that a large per- 

 centage of them are of inferior quality, or are con- 

 tained in deeper and thinner seams which cannot 

 be worked at the present cost"; whilst the rate of 

 consumption is increasing so rapidly that the output 

 of 236,000,000 tons of coal in 1905 had risen in 1907 

 to 267,8,^1,000 tons. 



Such factors as these mean an inevitable and in- 

 creasing rise in the price of coal, and it must be clear 

 that it will be the time when coal has risen to such a 

 price as seriously to hamper our power of competing 

 with other European countries that will govern the 

 period of our commercial supremacy, and not the date 

 of the complete exhaustion of our coalfields. 



Taking such figures as are available for the coal 

 resources of the more important coal-producing 

 European countries and the returns of the coal raised 

 in 1905 and 1907, we may tabulate them as follows : — 



Total e.\isting Coal raised 



United Kingdom 



Geimany 



France 



Belgium 



1 90s 



1907 



ial,inmillio 

 of tons 

 140,000 ... 236,130,000 ... 267,831,000 

 150,000 ... 119,349,000 ... 140,8^5,000 



17,000 ... 34,78o,coo ... 35,586,000 

 16,000 ... 21,500,000 ... 23,324,000 



So that for all practical purposes the quantity of coal 

 still existing in Germany may be taken as being the 

 same as ours, the extra 10,000 million tons which that 

 nation possesses being made up for by the superior 

 quality of our steam and gas coals. 



