SCIENCE. 



519 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No ?wtice is taken of anonymous communi- 

 cations.] 



To the Editor of Science. 



The " Ononid" meteors were watched this morning 

 from 12.20 to 3.05 by four observers. The shower seemed 

 quite abundant, 190 meteors being mapped during the 

 time of observation. About one-half of these undoubtedly 

 belonged to a common system. The radiant point as de- 

 duced from these, and which, considering their number 

 cannot be greatly in error, was R. A. — 86 , Dec. + 16 

 which brings it just outside tha limits of the constellation 

 Onon. No stationary meteors were observed and but 

 very few with short paths near the radiant point. This 

 may be due to the fact that they were so faint (mostly 

 about equal in brightness to a fourth magnitude star) that 

 the short paths were not sufficiently conspicuous to call 

 our attention to them. An auroral light was visible in the 

 north and east during the early part of the watch. 

 Chambers gives 85 ,+ 16 as the radiant point, and adds 

 thatTupman makes it 90 ,+ 1 1. 



Respectfully, 



Isaac Sharpless. 

 Haverford College Observatory, Pa., iomo, lqlh, 

 1881. 



DR. H. RAYMOND ROGERS AND HIS CRITICS, 

 To the Editor of " Science." 



Prof. Merriam, in your journal, page 495, writes as 

 follows : " I do not like to see so great an authority as 

 Faraday misunderstood, as he evidently is by your cor- 

 respondent on page 459 of your journal, and that, too, in 

 a way which he took particular care to caution against — 

 as to the law of gravitating action. That it acts inversely 

 as the square of the distance he fully believed and ad- 

 mitted ; or, to use his own words, T know it is so.' " 



The quotation objected to was made verbatim from 

 Faraday's writings, and the sentiments contained therein 

 were frequently expressed by him, and with emphasis. In 

 the work entitled " Correlation and Conservation of Force," 

 page 363, is an essay by Faraday entitled " The Conser- 

 vation of Force," in which we read the following, viz.: "I 

 believe I represent the received idea of the gravitating 

 force aright in saying that it is a simple attractive force 

 exerted between any two or all the particles or masses of 

 matter, at every sensible distance, but with a strength 

 varying inversely as the square of the distance. The 

 usual idea of the force implies direct action at a distance : 

 and such a view appears to present little difficulty except 

 to Newton, and a few, including myself, who in that re- 

 spect, may be of like mind with him. This idea of grav- 

 ity appears to me to ignore entirely the principle of the con- 

 servation of force ; and by the terms of its definition, if 

 taken in an absolute sense, ' varying inversely as the 

 square of the distance,' to be in direct opposition to it." 

 Again, in the same essay, page 366, " the assumption 

 which we make for the time with regard to the nature of 

 a power (as gravity, heat, etc.,) and the form of words in 

 which we express it, that is, its definition, should be con- 

 sistent with the fundamental principles of force generally. 

 The conservation of force is a fundamental principle ; 

 hence the assumption with regard to a particular form of 

 force ought to imply what becomes of the force when its 

 action is increased ox diminished, or its direction changed; 

 or else the assumption should admit that it is deficient on 

 that point, being only half competent to represent the 

 force ; and, in any case, should not be opposed to the 

 principle of conservation. The usual definition of gravity 

 as an attractive force between the particles of matter 

 varying inversely as the square of the distance, whilst it 

 stands as a full definition of the power, is inconsistent 

 with the principle of the conservation of force." 



. — 1 — 1 , ,. 



Faraday is here laboring to show the incompetency of 

 that definition alone. He thinks the natural philosopher 

 ought to look for effects and conditions as yet unknown; 

 and so virtually calls aloud for some one to fill up what 

 to him appears a serious deficiency. He called the old 

 definition only a //#^-assumption, and felt the necessity of 

 some enlargement of it, that it might stand secure. He 

 says : " the half-assumption is, in my view of the mat- 

 ter, more dogmatic and irrational than the whole, because 

 it leaves it to be understood that power can be created 

 and destroyed almost at pleasure." 



Faraday called for, what' we believe, the electric theory 

 amply supplies. Not only so, but he also indicated this 

 very source of supply. For example, a " grain of water " 

 having a given force of gravity has also "electric relations 

 equivalent to a very powerful flash of lightning." He 

 says, "It may, therefore, be supposed that a very large 

 apparent amount of the force causing the phenomena of 

 gravitation, may be the equivalent of a very small change 

 in some unknown condition of the bodies, whose attrac- 

 tion is varying by change of distance. For my own part, 

 many considerations urge my mind toward the idea of a 

 cause of gravity, which is not resident in the particles of 

 matter merely, but constantly in them, and all space." 



We have been led to think that it was not impossible 

 to find such " cause of gravity, not resident in the par- 

 ticles of matter merely," but which by means of a " very 

 small change in some [formerly] unknown condition of 

 the bodies," shall bring the whole subject of gravitation 

 out from the shadowy realms of darkness into abiding 

 sunlight. 



In brief, Faraday insists that the totality of the force 

 of gravity is not expressed by the definition that " grav- 

 ity acts directly as the mass and inversely as the square 

 of the distance." Indeed, he says as pithily as when he 

 uttered your correspondent's quotation, " I know it is 

 so." " That the totality of a force can be employed ac- 

 cording to that law / do not believe J" 



It might, by the way, be of interest to learn a little 

 more definitely as regards what it was that Faraday 

 knew was so. The following are his words : " That the 

 result of one exercise of a power may be inversely as 

 the square of the distance I believe and admit ; and I 

 know it is so in case of gravity." The same sentence, 

 however, continues : " but that the totality of a force 

 can be employed according to that law I do not believe 

 either in relation to gravitation or electricity or magnet- 

 ism, etc." 



It may be asked what can be correctly known of the 

 action of electricity or magnetism where the item polarity 

 is left out ? " What I object to," says Faraday, " is the 

 pretence of knowledge which the definition sets np when 

 it assumes to describe, not the partial effects of the force, 

 but the nature of the force as a whole." 



Satisfied with the old definition as your correspondent 

 may be, Faraday looked for a " missing link." We may 

 say that he pointed it out in saying : — " when we remem- 

 ber that the earth itself is a magnet, pervaded in every 

 part by this mighty power, universal and strong as 

 gravity itself, we cannot doubt that it is exerting an ap- 

 pointed and essential influence over every particle of 

 matter, and in every place where it is present. What its 

 great purpose is seems to be looming up in the distance 

 before us : — the clouds which obscure our mental sight are 

 daily thinning, and I cannot doubt that a glorious dis- 

 covery in natural knowledge and in the wisdom and 

 power of God in the creation is awaiting our age." 



I would conclude this part of my reply to your cor- 

 respondent, with the recommendation that he study Fara- 

 day, for " I do not like to see so great an authority as 

 Faraday misunderstood." 



Again, as regards the earth's return from aphelion to 

 perihelion : — 



It is admitted that my reply (p. 459) to Mr. Hendricks 



