July II, 1878] 



NATURE 'X- 



277 



i/i 



In glancing through the geological portion errors of 

 fact, such as that palms are oolitic, are seen to be nume- 

 rous. The confidence too with which the exact succession 

 of dicotyledons in geological time is set out is not war- 

 ranted by the present state of our knowledge. We read 

 the oft-repeated theory, now stated as fact, that Apctalce 

 preceded Polypeialce, and these Gamopetalce, That 

 this succession really took place, however probable 

 in itself, is, it is well known, far from proved. The 

 actual flowers discovered in the lowest eocene — almost 

 the oldest dicotyledonous flowers known — are Gamo- 

 petalous, and have been referred to Parana and Sym- 

 plocos. The abundance and differentiation of the 

 PapilionacecB, the Casalpinacea, and the Mimosce, show 

 how ancient are the PolypetalcB. Any preponderance 

 we may fancy the wind-fertilised Apetalce possess is due 

 to the fact that most of them are forest trees, and it is 

 the leaves of these which form the great mass of the 

 known dicotyledonous floras. Were those divisions 

 really produced in the sequence assigned them, the 

 origin of all alike is far older than the eocene and at 

 present unknown to us : so that even thus the writer of 

 the book is in error. 



A most unfortunate selection of illustrative genera of 

 eocene plants has been made. Azaleas did not abound 

 in the eocene, and have never even been met with in it. 

 Neither did the cactus nor aroids, since they have been 

 but recently noticed in the eocene, and then only in 

 England. In like manner the "peculiar" feature attri- 

 buted to the miocene, its gathering together in the same 

 flora plants now only found at immense distances apart, 

 is not a peculiarity of that formation, since it characterises 

 eocene floras in at least an equal degree. Chapter IV., 

 on the geographical distribution of flowers, deserves 

 especial mention, but must be consulted itself should 

 any one desire to learn (p. 80) how " the Proteacea 

 became Australian, the magnolias and tulip-trees chiefly 

 North American." 



Looking at the more botanical part of the book, it is 

 seen that the explanations of the modifications and 

 appliances of flowers to insure fertilisation are in some 

 cases not treated with the caution the subject requires. 

 To select an instance : the theory that white flowers open 

 more than any others at night, because they are the most 

 visible to moths, seems probable at first sight ; but the 

 unscientific reader, to whom the work is addressed, wish- 

 ing to see for himself, would reject it after his first walk 

 down a hedgerow at eventide, when he found the dog-rose, 

 the white convolvulus, and the daisy, all closed. Why, 

 too, Avhite flowers, if they rely upon their colour to attract, 

 should be also the most powerfully scented, is not ex- 

 plained. It is likely that perfumes would be more neces- 

 sary to the dark-coloured flowers which are open at night, 

 unless we suppose, which from experience we of course 

 should not, that only white flowers are fertilised by night- 

 flying moths. Persons whose experience of flowers is 

 confined to ordinary English gardens would remember 

 the heliotrope, the mignonette, musk, yellow azalea, 

 wall-flower, rose, coloured pink, hyacinth, violet, scented 

 verbena, scented geraniums, as the most highly-perfumed 

 plants, and would reasonably doubt that any exceptional 

 attractions in this respect belong to white flowers. In 

 comparison with perfume, the white colour may have 

 little to do with it, but Mr. Taylor must have remarked 

 that some law gives vastly superior brilliance to butter- 

 flies and day-flying moths and insects, and this law may 

 also require that flowers which only open at night should, 

 like insects which only fly at night, be white or compara- 

 tively very subdued in colour. J. S. G. 



Elements of Descriptive Geometry. By J. B. Millar, B.E. 

 (Macmillan, 1878.) 



Thanks to Messrs. Kempe, Hart, and other writers on 

 Linkages, we are able " Curvo dignoscere rectum," and 



" Parallels design Sure as Demoivre" could. The title of 

 the work before us shows that it is not concerned with 

 such elementary details as those which most naturally 

 find a place in works on practical geometry. Chasles in 

 describing the aim of Monge's great discovery, says: — 

 "La g^omdtrie descriptive, en effet, qui n'est que la tra- 

 duction graphique de la gdometrie gen^rale et rationnelle, 

 servit de flambeau dans les recherches et dans 1' appre- 

 ciation des resultats de la g^om^trie analytique ; et par la 

 nature de ses operations, qui ont pour but d'dtablir 

 une correspondance complete et sure entre des figures 

 eftectivement tracees sur un plan et des corps fictifs dans 

 I'espace, elle familiarisa avec les formes de ces corps, les 

 fit concevoir idealement, avec exactitude et promptitude, 

 et doubla de la sorte nos moyens d' investigation dans 

 la science de I'^tendue." Mr. Millar's book is a very 

 serviceable exposition of the subject as thus described, 

 and he has prefixed a short introduction on solid geo- 

 metry. A good English text-book on this branch (solid 

 geometry) is yet a desideratum. The plan on which the 

 figures ai-e arranged and drawn is, we think, likely ta 

 aid the student in his working out the propositions in the 

 text. 



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Hughes's Microphone 



Mr. Edison finds a resemblance between his carbon telephone 

 and my microphone. 



I can find none whatever ; the microphone in its numerous 

 forms that I have already made, and varied by many others 

 since, is simply the embodiment of a discovery I have made, in 

 which I coniider the microphone as the first step to new and 

 perhaps more wonderful applications. 



I have proved that all bodies, solid, liquid, and gaseous, are in a 

 state of molecular agitation when under the influence of sonorous 

 vibrations, no matter if it is a piece of board, walls of a house, 

 street, fields, or wood, sea or air, all are in this constant state of 

 vibration, which simply becomes more evident as the sonorous 

 vibrations are more powerful. This I have proved by the dis- 

 covery that when two or more electrical conducting bodies are 

 placed in contact under very slight constant pressure, resting on 

 any body whatever, they will of themselves transform a constant 

 electrical current into an undulatory current, representing in its 

 exact form the vibrations of the matter on which it reposes ; it 

 requires no complicated arrangement and no special material, 

 and to most experimenters the three simple iron nails that I have 

 described form the best and most sensitive microphone. But 

 these contact points would soon oxidise, so naturally I prefer 

 some conducting material which will not oxidise. 



Mr. Edison's carbon telephone represents the principle of the 

 varying pressure of a diaphragm or its equivalent on a button of 

 carbon varying the amount of electricity in accordance with this 

 change of pressure ; it represents no field of discovery, and its 

 uses are restricted to telephony. 



The three nails I have spoken of will not only do all, and that 

 far better than Edison's carbon telephone in telephony, but have 

 the power of taking up sounds inaudible to human ears, and ren- 

 dering them audible, in fact a true microphone ; besides it has 

 the merit of demonstrating the molecular action, which is con- 

 stantly occurring in all matter under the influence of sonorous 

 vibrations. 



Here we have certainly no resemblance in form, materials, or 

 principles to Mr. Edison's telephone. The carbon telephone 

 represents a special material in a special way to a special 

 purpose. 



The microphone demonstrates and represents the whole field 

 of nature, the aa hole world of matter is suitable to act upon, 



