I70 



NATURE 



IDc 



;, i8So 



often throws up clustering bunches of cane; that reacli a hei^^ht 

 of sixteen feet in one season. Associated with Ariindoconspiata 

 and Cyncciiim aygentum, the above interesting and handsome 

 plants give quite a tropical aspect to some of the hill-sides of 

 this no, them county. William Ingram 



Eelvoir, December 20 



The Appulse of Jupiter to 

 November 5 



Fixed Star on 



Refekring to a request appearinc; in Nature, vol. xxiii. 

 p. 158, I may say that the approach of Jupiter to li.D. + 2-97 

 was well observed here, and I found that the star, when perpen- 

 dicular to the belts, was 4"'05 distant from the northern limb. 

 ThR definition was good, and the measure, I should say, preily 

 exact. 



It was a strange and beautiful sight, Ju|iiler appearing with 

 five satellites, though, at Ibe same time, the different aspect of the 

 star compared with that of the moons was very striking. The 

 li<^ht of the former was however very sensibly affected by the 

 glow of the great disk near it, and i". looked no more than 10 

 magnitude. John Birmingham 



Jlillbrook, Taam 



British Earthquakes 

 May I ask leave to offer a few remarks on the leading article 

 on British Earthquakes which appeared in Nature, vol. xxiii. 

 p. 117. The author lirings out very strongly the apparent con- 

 neclion between great lines of jointing or faulting and earthquake 

 movements, and points out the great fault whicli traverses Scot- 

 land from sea to sea as a case in point. Now I had this same 

 question before the British Association this year, and exhibited 

 a map illustrative thereof. I had further, following up a theory 

 submitted by me to the Royal Irish Academy, on the Correlation 

 of Coast-Line Directions, and published by tliat body, drawn uii 

 on a Geikie's Geological Map of Scotland certain of those cor- 

 related lines, and on a smaller map of the British Isles had indi- 

 cated both the lines in question and the localities wherein earth- 

 quakes have been noticed in later times, more essentially since 

 1S60. One of those lines crosses the district about Comrie, and 

 at the moment (August, iSSo) could hardly be pointed out as in 

 any notable way supporting the connection sought to be esta- 

 blished between coast-line directions and eartliquake localities. 

 But the recent earthquakes in the north of Ireland and in .Scot- 

 land go far to do this, as the direction shown by me botli 

 agrees with the great fault mentioned by the author of the 

 paper on British Earthquakes in direction, and also fairly shows 

 the direction of the earthquake band or zone, which apparently 

 extends from Londonderry across Scotland. This direction is 

 exactly at 40° with the coast-line direction between Carnsore 

 Point and \Vicklow Head, as shown on the accompanying ma]i. 



I may add that having had occasion to examine Prof. Ilofer's 

 memoir on the " Erdbeben Kiirntens und deren Stosilinien," 

 and to compare his lines with those given on the map of Europe 

 exhibited by me at the British Association meeting of this year, 

 I find some very remarkable concordances as regards directions, 

 which, having .submitted to him, he quite recognised. I consider 

 theref re that this memoir. Prof. Geikie's very remarkable article 

 on the Volcanoes of North-Western Europe, and this late article 

 on British Earthquakes, all point more and more distinctly to the 

 importance of jointing and fissuring in connection with volcanic 

 and earthquake action, and so far go in support of the theory 

 submitted by me. J. P. O'Reilly 



Royal College of Sciences, Dublin, December 14 



A General Theorem in Kinematics 

 I AM very much obliged to Prof. Everett and Itfr. J. J. Walker 

 for having taken the trouble to point out that the theorem wliich 

 I communicated to Nature is, so far as it relates to utiiplanar 

 motion, already known. I am indebted to Prof. Unwin for more 

 complete information on the subject. He tells me that the 

 theorem (for the uniplanar case) has been employed by German 

 engineers in the discussion of stresses produced in moving pieces 

 — exactly the use of the theorem which naturally presents itself. 

 Moreover, the theorem (for the uniplanar case) will be found in 

 § 1 98 of Collignon's " Cinematique," as well as in other foreign 

 books, but not, so far a^ my information goes, in the work of 

 any English author. None of your correspondents or of mine are 

 however able to say that \\->.e. general case was previously known. 



The simple method of proof given by Prof. Everett is that 

 which I had used nearly a montli ago in a paper which I wrote 

 (and have si;!ce read) for the London Mathematical Society. 



I may mention in conneclion with tliis subject a kinematical 

 theorem which Mr. Kempe communicated to Nature some 

 time back. J find that this theorem corner properly under a 

 general theorem which holds for the areas of roulettes. It can 

 be easily proved that the areas of the most general kinds of 

 roulettes follow exactly the law of circular transformation which 

 .Steiner proved to hold good for the areas of pedals. For this 

 theorem of Steiner's see Williamson's "Integral Calculus," 

 p. 202, third ed. 



Mr. Kempe's theorem (as also Holditch's) is an immediate 

 consequence, since every possible uniplanar di- placement of a 

 body can be produced by cpicycloidal motion. Mr. Williamson, 

 justly describing Mr. Kempe's as " a singularly elegant theorem" 

 (ibid. p. 210), arrives at it quite differently. 



George M. Minchin 



Royal Engineering College, Cooper's Hill, December 13 



A Correction 



In Nature, vol. xxiii. p. 44, Prof. Young has published 

 some experiments proving that the thermo-electric power of a 

 platinum-iron couple is to be observed in vacuo as well as in air ; 

 this fact is said to be contradictory to the results given in my 

 papers. I presume that some error has caused this statement, 

 as I never and nowhere asserted that the thermo-electric power is 

 dependent on the surrounding gases. I have, on the contrary, 

 stated {Phil. Mag., October iSSo, p. 294) that no such influence 

 has been hitherto observed. Thus the experiments of Prof. 

 Young do in no way contradict my views. 



University of Vienna Fr.\nz Exner 



Jelly Fish 



On November 3, in the B.I. S.N. Co. 's steamer Arcot, Capt. 

 Stevenson, while in lat. 16° 50' N., long. 55° 45' E., with the 

 Kuriyan-muriyan islands to the north, thirtj' to forty miles and 

 three days out from Aden to Karachi, we passed through a vast 

 quantity of brown anemones, the ordinary bell shaped jelly-fish 

 and strange worm-like (apparently) jelly-fi-h, floating on and just 

 below the surface. These were first noticed about five in the 

 afternoon, and we were still amongst them when we went below 

 to dinner at six, the vessel steaming about eight knots. The 

 anemones were only peculiar in that they appeared to be rounded 

 at the base and without the ordinary flat surface for adhering to 

 rock or stone ; they were in vast numbers and had the feelers 

 expanded. The worm-like or centipede-like jelly-fish were from 

 six to eight feet long and as thick as a man's wrist. They 

 appeared sometimes singly, sometimes many twisted together ; 

 they were in slow feeble snake-like motion. All agreed that they 

 were ribbed in appearance ; but there was a difference of opinion 

 as to the colour. It was described by some as that of the sea, 

 by others as violet, brown, or purple. Each apparent rib was 

 divided from those next it by a bar of lighter colour. 



At night the sea was bright with many phosphoric lights of 

 many shapes, so we were perhaps still passing through the mass. 

 There was a dead calm at the time. 



The captain has read this account and stated it to be fairly 

 correct. F. C. Constable 



Karachi, Sind, November S 



MR. PLIMSOLLS CURE FOR COLLIERY 

 EXPLOSIONS 



LET us suppose a person actuated by very powerful 

 motives, who desires to solve the most difficult 

 mathematical problem of the da)', and who, after having 

 neglected to acquire the most rudimentary knowledge of 

 his subject, and after having contented himself with 

 seeking the company of land surveyors, and trying to 

 entrap civil engineers into conversations about it, sud- 

 denly startles the world with the cry of Eureka ! Eureka ! 

 Eureka I should we, or should we not, be inclined to 

 regard his solution with respect ? 



Mr. PlimsoU has done for the mining world exactly what 

 our suppositious person would have accomplished for the 

 mathematical one. In an article contained in the December 



