4 



NA TURE 



[November 7, 1895 



It is true that a very considerable space is devoted to the 

 history of the production of hybrid forms, and that an 

 account is given of the methods of securing successful 

 germination of spores ; but those who expect to find a 

 treatise on the cultivation of ferns per se, will not find 

 their hopes realised. 



The author again takes up cudgels in defence of his 

 views as to the existence of niiiltiple parentage^ a term used 

 to express his conviction that a single oosphere can be 

 fertilised by several antherozoids, or at the least, that a 

 number of fertilised oospheres on one prothallium can 

 influence the one which actually develops into a seedling 

 plant. It is true that some of the experiments adduced 

 by the author in support of his contention offer startling 

 results. Thus, if a pan be sown with the spores of, say, 

 four varieties, in a large percentage of the seedlings each 

 will exhibit resemblances to all the four forms, instead of 

 to only two, at most, of them. And this latitude of 

 variation exercised in the case of a single seedling is 

 stated to depend on the number of varieties which are 

 sown together, and not to accidental sports'. 



But the inferences thus drawn by the author are so 

 entirely at variance with the results of experimental 

 investigations on the higher organisms, that they will meet 

 with a cautious reception, at any rate, until the factors 

 which make up his results have been analysed and are 

 better understood. 



Whatever the ultimate verdict which will be passed on 

 the theoretical conclusions may be, the details of the 

 experimental basis on which they rest, provide interesting- 

 matter enough, and suggest fresh lines of investigation 

 which may well prove fruitful in results. 

 Vorlesungen aus der attalyfischen Geomeirie der 

 Ke^elschnitte. By Sigmund Gundelfinger. Edited by 

 Friedrich Dingeldey. 8vo. viii. + 434 pp. (Leipzig : 

 Teubner, 1895.) 

 The first part of this book (pp. 1-240) is an edition of 

 lectures on Conies delivered by Gundelfinger within the 

 last twenty years in the University of Tubingen and the 

 Technical School at Darmstadt. It contains a systematic 

 exposition of the analytical theory of Conies based on the 

 use of general homogeneous coordinates which are so 

 arranged that corresponding results in particular homo- 

 geneous coordinates and in ordinary Cartesian coordinates 

 can be written down from the results obtained. It also 

 contains an exposition of the theory of sets of Conies, in- 

 cluding four-point and four-tangent Conies, and nets and 

 webs of Conies. The theory is not written out with the 

 idea of enumerating all the independent concomitant 

 forms, but with the idea of expressing the geometrical 

 significance of the most important ones. The appendix 

 (pp. 240-426) contains solutions of problems on the sub- 

 jects treated in the first part. Many of the problems are 

 taken from the works of Steiner, some are original, and 

 not a few are difficult. A very complete index is given at 

 the end of the book. 

 Light. By H. P. Highton, M.A. Pp. 243. (London : 



Rivington, Percival, and Co., 1895.) 

 Books upon light are many and of various qualities, but 

 we think there is room for this little one. The subject 

 is treated in a very elementary manner, and is made 

 easy of comprehension by numerous diagrams. A further 

 good point possessed by the book is that the lessons 

 comprised in it are fully illustrated by experiments, all 

 of which are capable of being carried out by teachers 

 whose apparatus cupboards only contain a small stock 

 of materials for the demonstration of optical facts and 

 principles. The boy v/ho goes through a course such 

 as that described by Mr.- Highton, and who sees all the 

 experiments performed, will obtain a fair notion of the 

 laws of light ; and if he does the experiments himself, 

 he will benefit considerably by the manual and mental 

 training which his work will give him. 



NO. 1358, VOL. 53] 



LETTERS TO THE EDITOR. 



{The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous comrnunications. ] 



Curious Aerial or Subterranean Sounds. 



If the mysterious sounds referred to by Prof. G. H. Darwin 

 should turn out to be of subterranean origin, as is not unlikely 

 the case, it may be that they are the reports arising from the 

 process of "faulting" going on on a small scale at a great 

 depth, and not of sufficient intensity to produce a perceptible 

 vibration at the earth's surface. In this connection I may recall 

 an observation which bears upon the subject. When collecting 

 materials for the report on the East Anglian earthquake of 1884, 

 I was given a most circumstantial description of a loud 

 report which was heard by the chief officer of the coastguard 

 station at West Mersea during his watch between i.io and 

 1.20 a.m. on February 18 of that year. The sky was cloud- 

 less at the time, there was no flash such as might have been 

 expected if the sound had been due to thunder or the explosion of 

 a meteorite, and there was no artillery sufficiently within hearing 

 to account for the sound. This report heard by the coastguard 

 officer was afterwards found to have heenfelt as a slight shock at 

 a house which was very much damaged by the earthquake 

 which occurred a few weeks later (April 22), and we came to 

 the conclusion that the officer and the inhabitant of the house in 

 question had independently recorded a premonitory shock 

 (" Report," p. 40, by the writer, and W. White, " Essex Field 

 Club Special Memoirs," vol. i.). When Prof. Darwin's request 

 for information shall have led to further knowledge as to the 

 localities where the phenomenon has been observed, it would be 

 of great interest to have in such places instruments for recording 

 earth tremors. R. Meldola. 



November 3. 



Is it not possible that the " Berisal Guns" and "mist 

 poufifers," referred to by Prof. Darwin (p. 650), are merely 

 earthquake sounds, the attendant shock being too slight to be 

 otherwise perceptible ? Nearly all earthquakes are accompanied 

 by a rumbling sound, due, I believe, to the small and rapid 

 vibrations proceeding chiefly from the margins of the area over 

 which the fault-slip producing the earthquake takes place {Geol. 

 Mag., vol. ix.; 1892, pp. 208-218). In some districts (Comrie 

 in Perthshire, East Iladdan, in Connecticut, Pignerol in Pied- 

 mont, Meleda in the Adriatic, &c. ), sounds without shocks are 

 common during intervals which may last for several years, but 

 slight shocks with sound occasionally intervene, as if the sounds 

 and shocks were manifestations, differing only in degree and the 

 method in which we perceive them, of one and the same 

 phenomenon. In great earthquakes, the sound-area is confined 

 to the neighbourhood of the epicentre ; in moderate and slight 

 shocks the sound-area and disturbed area approximately coincide, 

 or the sound-area may even overlap the disturbed area. In the 

 limiting case, the disturbed area vanishes, and the vibrations are 

 perceptible only as sound. C. Davison.. 



Birmingham, November i. 



Thermal Conductivity of Rocks. 



In view of recent discussions in Nature anent the variation 

 of the thermal conductivity of different kinds of rock with the 

 temperature, the following results of an investigation, which has 

 been in progress for the last year in the Jefferson Physical 

 Laboratory, may be of interest. 



We have made observations upon piles of comparatively large 

 flat slabs of marble and slate by a form of " wall " method, and we 

 hope that we have determmed, with some accuracy, the internal 

 temperature gradient. 



We can detect no change in the conductivity of the block of 

 white Carrara marble which we have used between 0° C. and 



330° c. 



In the case of our slate, the conductivity in a plane perpen- 

 dicular to the cleavage increases about 25 or 30 per cent, 

 between 70° C. and 300° C. , the rate of increase being less rapid 

 at the higher temperatures. B. O. Pierce. 



Cambridge, Mass., October 20. R. W. Willson. 



