290 



NATURE 



Sjuly 29, 1880 



Key to the Universe; o>; a New Theory of its Mechanism. 

 Founded vpon a (i) Contimious Orbital Propulsion, 

 arising from the Velocity of Gravity and its Consequent 

 Aberrations ; (2) Resisting Ethereal Mediutn of Vari- 

 able Density, with Mathematical Demonstrations and 

 Tables. By Orson Pratt, Senior. Second Edition. 

 (Salt Lake City, Utah Territory, 1879.) 



Mr. Orson Pratt's work is not a text-boolc for students, 

 but an application of dynamical principles to the system of 

 the Universe. " The aim of the author is to vindicate the 

 UNIVERSALITY of the law {i.e., of gravitation) ; to rescue it 

 from the environed limits sought to be thrown around it, 

 and to give it that unlimited freedom of action which the 

 distinguished .'name 'universal' so appropriately and 

 definitely imports." Mr. Pratt states that astronomical 

 science needs a theory which will answer as far as pos- 

 sible nine questions, which he propounds ; the second is, 

 " Why do planetary bodies rotate upon their respective 

 a.KCs.'' Why do they rotate from west to east, instead of 

 the contrary direction .'' Is there any law governing their 

 diurnal periods ? " The ninth, " Will cometary orbits 

 ever be converted into those of a planetary form.'"' 

 " Unaided and alone, he launches his humble barque upon 

 this great unexplored ocean, with a compass of his own 

 invention." The discussion occupies thirteen chapters, 

 and his investigations result " in the development of the 

 following beautiful law : The cube roots of the densities of 

 the planets are as the square roots of their periods of 

 rotation." Without making any long comments of our 

 own we can say that Mr. Pratt's book gives evidence of 

 much hard work and, it may be, of ingenious speculation, 

 and we quote as appropriate to the work before us the 

 following remarks of Prof. Newcomb (" Popular Astro- 

 nomy," p. 233) : " It is true that many ingenious people 

 employ themselves from time to time in working out 

 numerical relations between the distances of the planets, 

 their masses, their times of rotation, and so on, and will 

 probably continue to do so ; because the number of such 

 relations which can be made to come somewhere near the 

 exact numbers is very great. This, however, does not 

 indicate any law of nature." 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts, A'o 

 notice is taken of anonymous communications, 



\The Editor tirgently rajucsts correspondents to keep their letters as 

 short as possible. Tlie pressure on liis space is so great that it 

 is impossible otherwise to ensin-e the appearance even of com- 

 munications containing intcrestim; and novel facts,'\ 



The Recent Gas Explosion 



The explosion of the gas iiiani in tlie neighbourhood of the 

 Tottenham Court Road appears to be an example on a large 

 scale of the phenomenon whicli occurs on the bursting of a 

 eudiometer. 



It is known (although I do not speak from experience) that 

 when such an accident happens the glass gives way at the surface 

 of the mercury in the tube, fur at this point the explosion is 

 most violent, in consequence of the gas being compressed by the 

 explosion of that above it. When no accident takes place the 

 flash of light is more brilliant at the surface of the mercury than 

 in the upper part of the tube. In order to see if this fact would 

 throw any light on the explosion of the gas main I tried a few- 

 experiments about a fortnight ago, an account of which may 

 possess some interest. A piece of combusticn tube I '93 m. long 

 and I3'5mm. in diameter was closed at one end, and at 100 mm. 

 from the open end of the tube a pair of platinum wires was 

 sealed into the glass. The tube was fdled over water with a 

 mixture of hydrogen and oxygen obtained by the electrolysis of 

 dilute sulphuric acid, and tlie mouth of the tube closed with 

 a plug of wet cotton wool. The tube was placed on the lawn 

 and secured to a heavy weight by a piece of string tied near the 

 open end; a spark from an induction-coil was then passed 



between the wires. The explosion of the gas blew out the plug 

 of cotton wool and bent the platinum wires against the sides of 

 the tube, but the glass was not broken. The tube was again 

 filled with tlie mixed gases and closed with a cork, which was 

 not forced tightly into the mouth of the tube. This time the 

 tube burst in the middle, leaving 78 m. of the closed end and 

 •59 m. of the open end without damage. The cork was projected 

 some distance, but the wires were not bent by the rush of gas ; 

 tlie closed end of the tube was only slightly moved from its 

 original position by the explosion. 



Another piece of similar tube, but only about -SS m. in length, 

 was next filled with gas and exploded in the same manner. The 

 closed end was burst, and -475 m. of the open end remained. 

 In this case the corl: was also projected, but the wires were not 

 bent. The experiment being made at night, it was noticed that 

 the flash was much more brilUant at the closed than at the open 

 end of the tube. A third tube of the same length as the first 

 was next tried ; the cork was blown out, but the tube did not 

 burst. It was again filled and the cork forced in tightly, but it 

 was again projected. The third time a block of stone was 

 placed a few millimetres in front of the cork ; this prevented its 

 projection, but the tube did not burst, being apparently of 

 thicker glass than the previous tubes. In the last three cases 

 the flash was brilliant in the half of the tube towards the closed 

 end. 



The explanation of the experiments seems to be, that in the 

 two tubes that burst the pressure produced by the explosion at a 

 distance of about three quarters of a metre from the point at 

 w hich the gas was fired was sufficient to overcome the resistance 

 of the glass ; and in the case of the long tube, which burst in 

 the middle, the release of the pressure prevented the closed end 

 from being destroyed. If the tube had been much longer there 

 would probably have been another place where the violence of 

 the explosion produced by the compression of the gas would have 

 burst the tube. 



The press of work at the end of the term has prevented my 

 carrying the experiments farther, but I intend to try the effect 

 of an explosion in a long lead or composition pipe, when 1 

 expect to find several swellings or burstings of the metal at the 

 points where the pressure is greatest. When the experiments 

 have been made I hope to be allowed to communicate them to 

 you. Herbert McLeod 



Cooper's Hill, July 24; 



The Freshwater Medusa 



In Nature, vol. xxii. p. 241, Prof. Lankester asserts that I 

 had in a previous number (vol. xxii. p. 21S) incorrectly repre- 

 sented him as holding that in Limuocodium the radial canals 

 terminate blindly, and as denying the presence of a marginal 

 canal. In proof of my inaccuracy he makes the following 

 statement : — 



"A reference to Nature, vol. xxii. p. 147, will show that in 

 my first publication on the subject I gave as a character of the 

 new genus, ' Kadiating canals 4, opening into the marginal canal. 

 Marginal or ring canal voluminous.' I made the same statement 

 in my communication to the Royal Society on June 17, and have 

 not since deviated from it." 



I have read tlie article to which Prof. Lankester here refers, 

 and which was published on the date of the reading of his paper 

 at the Royal Society. The ordy allusions in it to this subject 

 are the following : — 



" Radi.mtng Canals 4, terminating bUndly at the margin of 

 the disk." 



"Marginal or Ring Canal obUterated (or, if present, of 

 very minute size)." Geo. J. Allman 



Storm Effects 



The storms about this part of Surrey have been lately local 

 and violent, and the effects produced in some instances curious. 

 Visiting a neighbour's farm ou Wednesday evening (21st), we 

 found a field of standing wheat considerably knocked about, not 

 as an entirety, hut in patches forming, as viewed from a distance, 

 circular spots. 



Kxamin.d more closely, t'aee all presented much the same 

 character, viz., a few standing stall;s as a centre, some prostrate 

 stalks with their heads arranged pretty evenly in a direction 

 forming a circle round the centre, and outside these a circular 

 wall of stalks which had not suffered. 



I send a sketch made on the spot, giving an idea of the most 



