100 



KNOWLEDGE. 



[July 1, 1896. 



Mixvellaneoiis Papers. Bv Hciiirich Hertz Transliited by 1). K. 

 Joiips, B.Si\, and O. A. Soliolt, H.A., i3.Sc. (Mai'niillaii.) IIM. 



li'aler Snpplu. By W. 1'. Mason. (New York : 'Wiley. Lon- 

 don : (.'liajiiimn it Hall.) Illustrated. 2l9. 



A Dictiomini of the yames of Minerals. By A. It. Cliester, E.M., 

 Ph.D., So.D. (Xew York : Wiley. London ; Chnpiimn & Hall. 1 lOs. 



Pre.is Workinq of Metals. By Oberlin Smith. (.\ei\ York : 

 AViley. London: Clm)iman & Hall.) ]llu.«tnited. ]2s. (id. 



Chemi.itni in Daily Life. B^ Dr. Lassar-Colm, Translated by 

 M. M. Pnttison Muir, ALA. (avevel & Co.) Illustrated. (>s. 



A Manital of MenUini/ and Hepairint/. By C. Cx. Leland, (Chatto 

 & Windus.) Illustrated. 5s. 



-♦ 



[The Editors do not hold themselves responsible for the opinions or 



statements of correspondents.] 



SEA SICKNESS: A m'iCCII.\NICAL REMEDY. 



To the Kditom of Knowledge. 



Sirs, — Some years ago, when crossing the Irish Channel 

 on board a passenger steamer, with a very rough sea, it 

 oicurred to me that as the motions of the vessel produced 

 sea sickness, it might be possible to so utilize such motions 

 as to prevent that disagreeable malady. 



The vessel has three kinds of motion : a rising and 

 falling motion of the entire vessel ; an oscillatory motion 

 longitudinally about its centre of gravity ; and a transverse 

 rolling motion. 



Without going into the technicalities of these motions, 

 I may say that I treated the longitudinal motions as having 

 a tendency to drive matter, centrifugally, towards the head 

 and stern, and the rolling motions as having a similar 

 tendency to drive matter outwards from the centre of such 

 motions. 



Now, the entrance to the stomach is on the left side of 

 the body, the (rsophagus end, and the exit is on the right 

 side, the pyloric orifice ; and my experiment consisted in 

 utilizing the longitudinal motions so as to keep the food in 

 the stomach, and utilizing the rolling motions so as to 

 assist the natural operations of the wsophagus in propelling 

 the food towards the pyloric orifice. This I effected by 

 selecting a couch arranged in a line with the keel ; lying 

 with my head toiidida the engine room, and lying upon my 

 Ifft side. The experiment was entirely successful, and I 

 have always adopted it in rough seas, when a suitable 

 berth could be obtained. The pitching and rolling of the 

 vessel had the desired eiiect of aiding the retention of the 

 food, and the rising and falling of the entire vessel was 

 immaterial, and did not in the least interfere with my 

 comfort. The experiment cannot be carried out with 

 berths arranged athwart-ship. Thomas Moy. 



"waVes. 



To tlie Editors of Knowledge. 



Sirs, — Allow me to make a remark about Mr. Vaughan 

 Cornish's article on the " Tide Wave " in the May Number 

 of Knowledge. 



I find as explanation for the secondary tide formed by 

 the moon that the solid globe (that is, the earth as a 

 whole) is pulled away from the waters, leaving them 

 heaped up ; in other words, the earth is pulled out of its 

 orbit, in which it revolves once a year round the sun, and 

 undergoes a daily deviation (not a monthly one, which it 

 actually does), whilst the waters on the opposite side of 

 the earth are not subject to that deviation, because they 

 are not sufficiently attracted. That the attraction is less 

 powerful on the opposite side is quite true, but the con- 

 clusion I draw from this fact is different from that drawn 

 by Mr. Cornish. 



The large circle E represents the earth, the smaller M 

 the moon, and the shaded part round E the water 

 surrounding the earth, A and B being two points diametri- 



cally opposite on which there is high tide at the same 

 time. The attraction of the moon accounts for the wateru 



being heaped up at A, as the liquid mass is more subject 

 to that attraction than the solid earth. But is the earth 

 itself as a whole pulled away from its orbit in a daily 

 deviation ? Observation teaches it is not. So the solid 

 globe cannot actually be drawn away, and there must be 

 another reason for the water bulijing up at B. The 

 attractive power of the moon is much smaller at 15 than 

 at A, owing to the greater distance ; and therefore the 

 centrifugal force, which arises from the daily revolution of 

 the earth round its axis, has the same effect at B as the 

 attraction of the moon has at A — that is to say, owing to 

 the centrifugal force the waters at B try to get away as 

 far as possible from the centre of the earth, and cause the 

 same bulging out that takes place at A. 



I do not profess to have given in the above quite an 

 exact and correct statement of the facts. It seems to me, 

 however, more plausible than the theory of the solid globe 

 being pulled away from the waters. E. Wohlwill. 



TIDE OF the" RIVER WYE. 

 The second paragraph of Professor Logan Lobley's 

 note upon this subject in the List number of Knowledge 

 (at page IHO) was incorrectly printed. It should read as 

 follows : "A seismic wave, or one caused by a volcanic 

 eruption, although it may reach coasts at a great distance 

 if there is no intervening land, is non-coincident with the 

 cosmic tidal wave." 



ABOUT DEATH RATES. 



By Alex. B. M.\(I)owall, M.A. 



WE live in an age of sanitation. In the course 

 of a generation the conditions of life have in 

 some ways been sensibly improved. It is a 

 well-known fact that the death rate has de- 

 clined. This result has naturally been an 

 occasion for much — perhaps excessive — ^jubilation. There 

 are sanguine spirits who seem to see in the near futm-e a 

 complete victory over all the ills that Hesh is heir to. 



It is not so generally known that this improvement in 

 the death rate is not an all-round one ; that is to say, it 

 holds good only, as we may put it, for the earlier half of 

 life. The death rate of middle-aged and elderly people has 

 increased. I will illustrate this with a diagram (Fig. 1). 



This relates to males, in England, of different age- 

 groups, viz., to 5, 45 to 55, 55 to 65, and 65 to 75. 

 The first dotted curve shows the variation in the death 

 rate of children. By a smoothing process the general 

 course of the curve is brought out more clearly in the 

 continuous curve, each year-point of which represents an 

 average of ten {e.g., that for 1818 the average of 1841 to 

 1853). Here we find a marked decline from about 1865. 



When we come to the age-group forty-five to fifty-five, 

 however, we encounter a general rise in the death rate ; 

 and the next two decade- groups (for which only the smooth 

 curves are given) are of the same type.* 



With regard to the omitted age-groups, the earlier ones, 

 to thirty-five, all show a decline, and generally from the 



* Each of these curves, or curve-groups, it will be seen, has its 

 separate scale, and that of « is different from those of h. c, and d. 



