4i 



♦ KNOWLEDGE ♦ 



[July 20, 1883. 



I can but refer very briefly to the results of the manuring 

 experiments, but as they are in most parts similar, as I said 

 before, to those needed for the potato, this wiU, I hope, be ex- 

 cusable. But I have already taken up so much of the editor's 

 space, that I am afraid he will be " hauling in the slack " if I do 

 not stop very soon. 



The French sugar manufacturers prohibit the use of nitrate of 

 sodium among the growers of beet, presumably on account of beet 

 absorbing such large quantities of nitrates from the soil. In fact, 

 it is thought that the food of an animal kept on English beets 

 manured with this salt would contain such an amount of nitre as 

 would be really injurious ! 



It is better to apply artificial manure containing nitrogen-phos- 

 phates and potash in a soluble form shortly before the seed is 

 sown. 



Beets which contain the most sugar are poor in nitrates ; hence 

 nitrates decrease the yield of sugar. 



There is a parasite called Heterodera Schechtii, which causes a 

 failure in the crop ; before this fact was discovered, the failure was 

 put down to absence of potash and poorness in the soil. 



The potash of charcoal residues is in a form which can be more 

 readily absorbed by the beet than the potash of molasses beet. 

 Phosphates and guano give very favourable results as regards the 

 percentage of sugar in the yield. Lime from sugar works is 

 better for the sugar manufacturer, as manure, than the mixture of 

 lime with distillery residues. 



Avoid slow working manures, for it must always be borne in 

 mind that all delays which prevent the plant from reaching its full 

 growth are at the expense of the saccharine matter of the roots ; 

 they go on gi-owing and taking up salts from the soil which they 

 have not power to assimilate. Phosphates are most favourable 

 when applied in the spring. 



Stable-dtrng, when applied to the fields in the autumn, yields ver3- 

 good results both in quality and quantity. The use of phosphates, with 

 Chili saltpetre, gave very favotirable results — such good ones, in fact, 

 that it is thought that farmers would do ■\\Tong to continue the use of 

 nitrogenous manure alone. Two parts of Chili with thi'ee of super- 

 phosphate is a good mixture, but the best mixture of this must be 

 deduced from future experiments, for which we must wait until we 

 see the reports of the work now being carried on. 



Another good mixture is 20 kilos, of phosphoric acid and 10 kilos. 

 of nitrogen manure. 



This, I hope, is enough new matter for the consideration of your 

 readers, without my going into further details on this, at least to 

 me, very interesting subject. F.C.S. 



A CORRESPONDENT of the Nebraska State Journal writes : 

 " I wish I could give you a description that would do 

 justice to a railroad I rode on in Oregon. There used to 

 be some coal-mines up at Coquille City, and a wooden 

 tramway was run up from the head of Coos Bay. The 

 mines gave out, but the tramway was left I heard there 

 was a railroad, and when I got there the train had backed 

 up to the end of the track. "Well, you would have died to 

 see that train of cars. The old man who had appropriated 

 the tramway had got an old engine out of the mine and 

 mounted it on a hand-car, and connected the driving-shaft 

 with the handle. This was the engine and tender. The 

 baggage, mail and express cars, and the passenger coaches 

 were comprised in two rulAile cars, such as are used in 

 the section for carrying tools, rails, &c. The old man was 

 a no less wonderful combination than the train. He was 

 the company and the working force of the road. President, 

 vice-president, stockholders, agent, conductor, engineer, 

 fireman, and peanut boy were all comprised in his lank 

 form. He never had any trouble with the stockholders, 

 and he carried the general office in his hat. My fellow 

 passenger raised an umbrella when he got on board, and on 

 my inquiry as to the need of an umbrella, said I had better 

 raise mine — I would need it. When the train started I 

 found out he was right. The puffing, wheezy old engine 

 sent soot and water over us in a perfect shower. We got 

 along, however, very well, and would have made the trip 

 as quickly as we could have walked it, if the train had not 

 stopped when we were about half way, and waited half- 

 an-hour for a man who wanted to go with us to finish his 

 supper." 



" Let Knowledge grow from more to more." — ALrBED Tennyson. 



Only a small proportion of Letters received can possibly he in* 

 serted. Correspondents must not be offended^ thereforej should their 

 letters not appear. 



All Editorial commujiications sho^dd be addressed to the Editor of 

 Knowledge ; all Business communications to the Publishees, at the 

 Office, 1i, Great Queen-street, W.C. If this is not attended to, 



DELAYS ABISE FOR WHICH THE EDITOR IS NOT EESPONStBLE. 



All Remittances, Cheques, and Post Office Orders should be made 

 payable to Messrs. Wyman & Sons. 



The Editor is not responsible for the opinions of correspondents. 

 No communications are answered by post, even though stamped 



AND directed envelope BE ENCLOSED. 



FLIGHT OF MISSILES. 



[874] — As to the westward deviation of a vertically discharged 

 projectile caused by the rotation of the earth, Mr. Bray's investi- 

 gation seems at first sight to be demonstrative, and, from its ability, 

 thoroughly deserves to be so. Probably he has by this time dis- 

 covered the deficiency therein. Let a mean always the place of 

 discharge on the earth's surface, whatever position it may occupy 

 in absolute space. We are on the equator, and jj Tirginis is in the 

 zenith at the instant of discharge ; so that our vertical at that 

 instant is in the direction of arj- Now, Mr. Bray has taken into 

 consideration only that the eastward angular movement of the 

 vertical round a leaves a i; and the projectile to the westward ; he has 

 overlooked that this same movement brings the centre of the earth 

 and the direction of gravitation to the westward of the downward 

 prolongation of at], and that therefore the projectile must be, at 

 any time after discharge, not only west of the vertical, but, even 

 more, westward of arj. I believe that he is better able than I am 

 to complete his calculation by the introduction of this element. 



If t be the whole time of flight, your formula for the deviation, 

 Ci„ of a projectile, due to the height attained and the time of flight, 



becomes c* = h cos X. It is quite easv to make out the 



3 P 

 formula for the deviation, c,, due to the range attained and the 



time of flight, which is S, = 2jr — r sinX; the former deviation being 



always to the west, the latter in northern latitudes to the right. 

 Substituting for h its value from tie theory of parabolic trajec- 

 tories, ' '''^'°'' . and for r, 2f' sm t cos t ^^. ^^^^^ Telocity and t elc- 



2;7 P 



vation of discharge), we havec, : f, :: tane : 3tanX. Whence follows 

 the interesting but not generally known result that in firing dne N. 

 in northern latitudes, when the two deviations are in opposite 

 directions, if e be selected so that tan ( = S tan X, they will be equal 

 and will annul each other. Thus, if the resistance of the air were 

 absent, a shot fired N. from Westminster Bridge at the elevation of 

 75° 9' would have no deviation from the rotation of the earth. 



M. E.G. 



BINOCULAR VISION. 



[875] — My first letter having elicited comment, as I hoped, I beg 

 to be allowed space for a few words in reply. I marvel much at 

 some of the contents of Mr. Browning's criticism. Of course, I 

 accept his statement of spectacles with unequal lenses being com- 

 fortably and satisfactorily used in a case of disparity of vision 

 between the right and left eye of the wearer. But I take leave to 

 observe that, in the case referred to, the linear disproportion (40 to 

 16) is only as 2i to 1, whereas in my case (36 to 5) it is more than 

 7 to 1. No just parallel can, therefore, be drawn. As to the mis- 

 take with which he credits me, I remain unconvinced ; he quotes 

 ray opinions as being that two " well-defined images of different 

 dimensions will not coincide and coalesce " ; whereas I used the 

 word "immensely " before different, which is immensely different. 

 The example which he gives of a penny and halfpenny seen in the 

 "stereoscope" [misprinted "spectroscope"], is, similarly, not a 

 case in point, the disproportion between the coins not being suffi- 

 ciently marked. Had he made the experiment, say, with a crown 



