342 



NATURE 



{Feb. 12, 1880 



magnet, which in this new form is vertical and pro- 

 vided with unusually massive cheeks. One detail of 

 construction is, however, singular, though it seems to 

 have escaped the notice of electricians. Beneath the 

 longitudinal strands of covered wire the central core of 

 the armature, which is of wood, is overspun with a few 

 layers of iron wire wound transversely. This layer of 

 iron resembles in a kind of way the iron ring in the 

 armature of the Gramme machine, and though no con- 

 ducting wires traverse the interior of it, it clearly may 

 serve one of the important functions of the iron ring in 

 the Gramme machine in concentrating the lines of force 

 in the field. In support of the allegation that this 

 machine gives out in electricity 90 per cent, of the energy 

 it receives from the driving engine, Mr. Edison caused 

 certain calculations by Mr. Upton to be published in the 

 Scientific American. We have examined these calcula- 

 tions and find that they are based on the supposition that 

 the electromotive force of the generator is a constant 

 quantity when the speed of revolution is constant, and 

 independent of the resistances of the circuit and of the 

 quantity of current generated. This can only be true if 

 the field magnets are excited by a separate current and 

 o-enerator. Now, in the numerical calculations which 

 have thus been put forth in proof of the above assertion, 

 there is no statement made as to the power necessary to 

 supply this auxiliary current, nor indeed are any statistics 

 whatever given of the actual power (in foot pounds or any 

 other measure) delivered by the driving engine to the 

 generator ; only a cut-and-dry calculation to show that if 

 the external resistance be greater than the internal the 

 machine will theoretically work more economically when 

 not generating the maximum current ! In the Scribner 

 article it is explicitly stated that a second Faradic machine 

 is used to render active the magnets of the machine which 

 supplies the light, and in two admirable pictures, one of 

 which is a view of the battery of Faradic machines set up 

 in a " central station," the nature of the arrangements is 

 shown. 



We need not refer in detail to the enthusiastic incon- 

 sistencies in the Times correspondent's accounts. Upon 

 Edison's own data, electricity, instead of costing one- 

 fortieth of the price of gas, costs at least seven-eighths 

 as much, or about thirty-five times as dear as the Times 

 correspondent declares. As to the cost of the lamp itself, 

 with its carefully incinerated horseshoe of paper, its glass 

 globe exhausted to one-millionth of an atmosphere, and 

 its platinum-connecting wires, we confess we do not know 

 where the work could be done for anything like the cost of a 

 shilling. " The current can be transmitted on wire as small 

 ;\s No. 36," says the Times reporter, who, probably being 

 unaware that the resistance of a yard of such wire is at 

 least half an ohm, avoids saying what length of such wire 

 may be used. With a generating machine " in a central 

 station, perhaps a half-mile away," the introduction of 

 400 ohms' resistance would be serious — to the light. 



But apart from the mild absurdities of newspaper cor- 

 respondents, the more we study the detailed accounts of 

 the new inventions the more we regret that Mr. Edison 

 does not devote some time to learn what has been already 

 done in this field. An inventor who ignores what has been 

 done ought not to be mortified to find himself occasionally 

 forestalled by others in some discovery which he prides 



himself is his own. Possibly this may explain the inability 

 sometimes shown by an inventor to credit the good faith 

 of a rival who has priority. The worst feature of such a 

 course of thought lies in its absolute incompatibility with 

 a truly scientific spirit. Here the scientific man and the 

 inventor part company ; since the habits of accurate 

 thinking and the necessary candour of the scientific 

 method preclude the truly scientific man from ignoring, 

 even for the sake of scientific discovery, that which is 

 already a part of scientific truth. We are doing no 

 injustice to Mr. Edison's splendid genius when we say- 

 that it is to the character of the inventor, not to that of 

 the scientific thinker, that he aspires. 



What shall we say, finally, to the whole system of these 

 reckless newspaper announcements — for which, as we have 

 said, we ought not to hold Mr. Edison responsible — by 

 which the public mind is periodically fluttered ? 



The remedy to these things is obvious enough. Let 

 scientific men once and for all repudiate these false and 

 unwholesome displays of ignorance. Let public opinion 

 insist that the inventor shall be allowed to pursue his 

 way unhampered by the officious interference of the 

 unprincipled speculators whom his soul abhors, or by 

 the irrepressible unscientific reporter who is only one 

 degree less reprehensible for the part he plays. Whether 

 the latest forms of the invention are doomed to the fate 

 of their predecessors or not, the man who can struggle 

 against failures and discouragements as indomitably as 

 Edison has done deserves to succeed, however erratic his 

 methods. But if he succeeds ultimately, it will be in 

 spite of the vampires of the Stock Exchange and the 

 hangers-on of the New York press, who dog his steps 

 for their own selfish ends. 



THE MOTION OF FLUIDS 

 A Treatise on the Mathematical Theory of the Motion 

 of Fluids. By Horace Lamb, M.A., formerly Fellow 

 and Assistant Tutor of Trinity College, Cambridge ; 

 Professor of Mathematics in the University of Adelaide. 

 (Cambridge University Press, 1879.) 



NOT the least part of the good that must be attributed 

 to the publication of the first volume of Thomson's 

 and Tait's " Natural Philosophy " is that, as in the cases of 

 Maxwell's " Electricity " and Lord Rayleigh's "Sound," it 

 has led and prepared the way for the complete revision and 

 Teat advancement of several branches of mathematical 

 physics at the hands of those who have made a special 

 study of these branches. Lamb's " Theory of the Motion 

 of Fluids" must be looked upon as another, and lor the 

 most part a worthy, offshoot of this wonderful volume. 

 Although it would be too much to expect that one so 

 young as Mr. Lamb should display the same masterly 

 knowledge of his subject as has been displayed by the 

 authors of the two previously-mentioned wor^s, still the 

 thoroughness with which the very difficult and somewhat 

 extensive literature has been handled, and the apprecia- 

 tion of the mathematical points displayed by the author, 

 together with a rare facility in abbreviating and express- 

 ing, render this in most respects about the best possible 

 text-book of which the present state of the subject admits. 

 Having said this, it will be seen that I do not make 

 the following remarks with any view of disparaging the 



