>/K4, ^^7^1 



NATURE 



249 



LETTERS TO THE EDITOR 



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The Phonogfraph 



I HAVE received the following interesting letter from Dr. 

 Blake, Boston, U.S.A. :— W. H. Preece 



" You may possibly be interested in some recent experiments 

 which I have made with the phonograph, and unless you 

 have been pursuing the same course, may find them worthy of 

 repetition. 



"I found that the groove in the cylinder, covered with tin- 

 foil, became a resonator for the high scratching noise of the em- 

 bossing point, materially interfering with the reproduction of the 

 quality of the voice. 



" By stretching a thin layer of rubber tissue over the cylinder 

 this resonating effect was done away with and the scratching 

 noise materially lessened. This experiment was new to Mr. 

 Edison, and has since been repeated with like success. 



"Since experiments made with the ferrotype telephone and 

 phonograph-discs show that they transmit with almost astonishing 

 accuracy the lighter over-tones of the human voice, but at the 

 same time give especial prominence to certain over-tones to 

 which the metal disc especially responds, I constructed a dia- 

 phragm upon the principle of the human drum membrane, to be 

 used as a reproducing disc ; the object being to employ a mem- 

 brane which, from its structure and shape, would reproduce the 

 lighter over-tones representing the quality of the voice, and at 

 the same time ' cut off ' the sharper exaggerated over-tones 

 embossed as such by the metal disc upon the tin-foil. The 

 results of the experiments with such a membrane were very 



A small rod of light pine wood having a rubber pad at either end is placed 

 between the boss which carries the embossing point and the centre of the 

 membrane. This, the first form of disc constructed, worked very well. 



gratifying. After embossing with the metal disc, the curved 

 membrane was substituted, and the voice reproduced from the 

 phonograph without the sharper over-tones, with much more 

 natural and agreeable quality and with more than double inten- 

 sity. On using the curved membrane for embossing as well as 

 reproducing, I found, as would be expected, that the quality of 

 the voice was more accurately represented, and that the embos- 

 sing could be done at a distance of over fifteen feet from the 

 phonograph, and be reproduced with clearness. 



" Mr. Edison is now experimenting with this form of dia- 

 phr^fm, and, I understand, with very good results. 



" The material used for these discs may be either stout felted 

 paper (to be varnished on the outer surface when used for speak- 

 ing) or drum-head, moistened and pressed into concave form 

 before using. The principle governing the vibrations of such a 

 disc is that of imparting the vibrations to the centre of a mem- 

 brane the curve of which enables it to reproduce a large range 

 of over-tones, its tension serving as a counterbalance to the 

 central pressure. " Clarence T. Blake 



"W H. Preece, Esq., London." 



Physical Science for Artists 



- With reference to Mr. Norman Lockyer's and Prof. Briicke's 

 observations on the appearance presented by the shadow of the 



earth at sunset or sunrise (Nature, vol. xviii. p. 223), I beg to 

 be allowed to confirm them by my experience in Switzerl^d. 

 Early starts for expeditions give one, among other good things, 

 opportunities for seeing sunrise from the very beginning, and I 

 have repeatedly seen the shadow of the earth, as it were, 

 gradually driven do^vn by the illuminated portion of the sky, the 

 boundary between them being very well marked and roughly 

 circular like the horizon, but I think with a greater apparent 

 curvature. At this distance of time (some years) I cannot 

 remember anything of an effect of foreshortening such as Prof. 

 Briicke notices. 



Once, in 1868, I saw an even more curious effect. As we 

 stood at sunrise on a moderately sharp ridge running pretty 

 closely north and south, at a height of 9,000 to 10,000 feet, 

 there was an interval of appreciable duration in which it was a 

 visible and striking fact that it was night on one side of the 

 ridge and day on the other. F. Pollock 



Savile Club, Savile Row, W., June 27 



Cyclones and Anticyclones 



I WILL endeavour to put into a ^v^itten form the ideas 

 which have occurred to me respecting the law which, as I sup- 

 pose, connects and governs the atmospheric phenomena which I 

 see referred to in the newspapers as cyclones and anticyclones. 

 I have seen it stated, as the result of observation, that in what- 

 ever direction the wind may be blowing at any given time, if 

 you place your back to it the barometer will be found to stand 

 lower upon your left than upon your right. I have also seen it 

 stated that what are termed cyclones are rotatory movements of 

 the air occasioned by the meeting and passing one another of 

 two currents of air moving in opposite, or nearly opposite, direc- 

 tions, and that these cyclones or rotatory storms, though differ- 

 ing much in area, have certain featiu-es common to most, if not 

 all, of them ; namely, that the direction of their rotation is from 

 right to left, or, in other words, the opposite of the motion of 

 the hands of a watch, and that in their centre' is found a con- 

 siderable diminution of atmospheric pressure. On the other 

 hand, in what is termed an anticyclone, the direction of the 

 rotatory movement is in the opposite direction, that is, from left 

 to right, or in the same direction as the movement of the hands 

 of a watch, while in the central region the barometer is found to 

 be standing high. 



These various phenomena appear to me to be closely connected 

 one with the other, and to be, in fact, due to the rotation of the 

 earth upon its axis, which, having regard to its spherical form, 

 makes it inevitable that the superincumbent air at the equator 

 must rotate with the earth imder it at a much greater velocity 

 than that which is near the pole. For it seems evident that a 

 cxurent of air coming from the north travels into a region which 

 is moving to the east more quickly than itself, and will therefore 

 present itself as a north-east wind to the inhabitants of the more 

 northern latitude, and not only so, but ^vill tend to arrest the 

 air on its right or westerly hand, while it is left or abandoned 

 by the more quickly eastward-moving air on its left or easterly 

 hand. This consideration will explain, so far as northerly winds 

 are concerned, the first-mentioned of the phenomena above 

 referred to, namely, the lower glass on the left hand, the 

 higher glass on the right. Taking next the case of a nor- 

 therly ^vind, it will be obvious that in travelling northward 

 it comes to a country moving westward more slowly than-. 

 itself, and consequently appears as a north-west wind to 

 the people over whose land it passes ; and not only so, but by 

 pressing on the air to the right, or eastward side, it increases 

 pressiu-e in that direction, while it tends to leave behind the more 

 slowly moving air on its left, or westward side, thus again 

 producing the first -mentioned phenomenon of a high glass on 

 the right and a low glass on the left, so far as southerly winds 

 are concerned. If this principle is considered with reference to a 

 cyclone and the direction of the rotatory movement is also taken 

 into account, it seems to be made clear that a cyclone is occa- 

 sioned by the meeting and passing each other of a northerly and 

 southerly current so that they pass each other on the left hand 

 respectively. 



When this occurs the low pressure on the left or east side of 

 the north wind coincides with the low pressure on the left or 

 west side of the south wind, and thus a depression is formed 

 round which the wind rotates. It follows that the west and 

 south wind is found in the south and south-east side of the storm, 



