128 



SCIENCE. 



[Vol. XVII. No. 422 



zontally under and near the plastered ceiling of that second 

 floor, till it came near a plastered wall ; then down by the 

 side of that wall to a clock, which stood about twenty feet 

 below the bell. The wire was not bigger than a common 

 knitting needle. The spire was split all to pieces by the 

 lightning, and the parts flung in all directions over the 

 square in which the church stood, so that nothing remained 

 above the bell. The lightning passed between the hammer 

 and the clock in the above mentioned wire, without hurting 

 ■either of the floors, or having any effect upon them (except 

 making the gimlet-holes, through which the wire passed, a 

 little bigger), and without hurting the plastered wall, or any 

 part of the building, so far as the aforesaid wire and the 

 pendulum-wire of the clock extended; which latter wii*e was 

 about the thickness of a goose-quill. From the end of the 

 pendulum, down quite to the ground, the building was ex- 

 ceedingly rent and damaged. . . . No part of the aforemen- 

 tioned long, small wire, between the clock and the hammer, 

 «ould be found, except about two inches that hung to the 

 tail of the hammer, and about as much that was fastened to 

 the clock; the rest beiug exploded, and its particles dissi- 

 pated in smoke and air, as gunpowder is by common fire, 

 and had only left a black smutty track on the plastering, 

 three or four inches broad, darkest in the middle, and fainter 

 towards the edges, all along the ceiling, under which it 

 passed, and down the wall." 



Mathematical Theory. 



There is stored up in each cubic centimetre of the column 

 of dielectric from the cloud to the earth, just before the 

 lightning-discharge, an amount of electrical energy given by 



the expression — i^£J^ where K is the specific inductive 



capacity of the dielectric air, and ^ the electro-motive in- 

 tensity, both in electrostatic units. This expression is given 

 on p. 156, Vol. I., second edition, of Maxwell's "Treatise on 

 Electricity and Magnetism." Substituting the values of K 

 and E (remembering, of course, that they are in electrostatic 

 units), and reducing, we find that the amount of energy in- 

 volved amounts very nearly to one foot-pound for each cubic 

 foot of air involved. If we consider that the dissipation of 

 this electrical energy takes place throughout the whole length 

 of the column of dielectric from the cloud to the earth, we 

 shall see that all the energy that we have to care for in our 

 lightning-rod is that existing in the section of the column 

 contained between two horizontal planes passing through 

 the top and foundation of our house respectively. This may 

 not, of course, be strictly true, but it must be essentially. 



No reason can be assigned why the electrical energy 

 should disappear at the top, or at the bottom, or at the centre, 

 of the column of dielectric in which it exists, so that it is 

 reasonable to maintain that what we call a lightning-flash is 

 simply a line of air in which the electrical energy is being 

 dissipated as heat. The energy, therefore, is transmitted, 

 not from the cloud to the earth or from the earth to the 

 cloud, but horizontally from all portions of the dielectric to 

 some central core where it appears as heat, and where the 

 phenomenon we call a lightning-flash is manifested. 



One result of this consideration is, that, in order to pro- 

 duce the amount of energy which is known to exist in 

 Jightning-discharges, the radius of the column of dielectric 

 at the surface of the earth must be very considerable, in 

 order that there shall be a sufficient mass of air to furnish, 

 at the rate of one foot-pound per cubic foot, enough energy 

 to produce the well-known results. N. D. C. Hodges. 



ARISTOTLE AS A NATURALIST.' 



Having had occasion of late years to make myself acquainted 

 with the observations and ideas of ancient writers upon matters 

 connected with natural history, and having been thus more than 

 ever impressed by the unique position which in this respect is held 

 by Aristotle, it appears to me that a short essay upon the subject 

 may prove of interest to readers of various kinds. Therefore, as far 

 as space permits, I will render tlie results of my own inquiries in 

 this direction; but, as it is far from an easy task to estimate with 

 justice the scientific claims of so pre-scientific a writer, I shall be 

 greatly obliged to more professed students of Aristotle if they will 

 indicate, either publicly or privately, any errors of fact or of judg- 

 ment into which it may appear that I have fallen. 



Aristotle died B.C. 323, in the sixty-third year of his age. As 

 a personal friend and devoted pupil of Plato, — who, in turn, was 

 a friend and pupil of Socrates, — his mind was at an early age 

 brought under the immediate influence of the best thinking of 

 antiquity. Nevertheless, although entertaining a profound ven- 

 eration for his master, like a true devotee of truth, he did not 

 allow bis mind to become unduly dominated even by the authority 

 of so august a tutor; and in after-life he expressly broke away 

 from the more mystical principles of Platonic method. While 

 still a young man, he was invested with the magnificent office of 

 educating Alexander the Great. He held this position for a period 

 of four years, and then the young prince, at the age of eighteen, 

 became regent. It is interesting to note that the relations which 

 subsisted between this greatest philosopher and this greatest gen- 

 eral in the world's history were throughout relations of warmest 

 friendship. Indeed, had it not been for the munificent aid which 

 was afterwards given by Alexander, it would have been impossi- 

 ble for Aristotle to have prosecuted the work which he accom- 

 plished. 



Questions have been raised, not only as to the authenticity of this 

 work, but also as to the originality of much that is undoubtedly au- 

 thentic. Into these questions, however, I need not go. Whether or 

 not Aristotle borrowed from other writers without acknowledgment, 

 it is certain that in his writings alone are preserved the records of 

 early biological thought and observation, which would otherwise 

 have been lost; and the preservation of these records is of more 

 importance for our present purpose than is the question to whom 

 such thought and observation were in every case due. 



Whether we look to its width or to its depth, we must alike 

 conclude that the range of Aristotle's work is wholly without a 

 parallel in the history of mankind. Indeed, it may be said that 

 there is scarcely any one department of intellectual activity where 

 the mind of this intellectual giant has not exerted more or less 

 influence, in some cases by way of creation, in others by way of 

 direction. The following is a list of the subjects on which Aris- 

 totle wrote: physics, astronomy, meteorology, zoology, compara- 

 tive anatomy, physiology, and psychology; poetry, ethics, rhetoric, 

 logic, politics, and metaphysics. Of these subjects he was most 

 successful in his treatment of the second series as I have arranged 

 them, or of the more abstract and least rigidly scientific. In his 

 " Politics" he gave the outlines of two hundred and twenty-five 

 constitutions, and, although but a fragment of his whole work in 

 this direction has come down to us, it is still regarded as one of 

 the best treatises that has ever been written on the subject. His 

 "Ethics," "Rhetoric," and "Logic," also, still present much 

 more than a merely historical interest, for he may be said to have 

 correctly laid down the fundamental principles of these sciences, 

 his analysis of the syllogism, in particular, having left but com- 

 paratively little for subsequent logicians to complete; and, lastly, 

 his " Metaphysics " alone would have been sufBoient to have 

 placed him among the greatest thinkers of antiquity. 



That his labors in the field of more exact science should not 

 now present a comparable degree of value, is, of course, inevita- 

 ble. At the time when he wrote, the very methods of exact 

 science were unknown; and I think it constitutes the strongest of 

 all his many claims to our intellectual veneration that he was able 

 to perceive so largely as he did the superior value of the objective 

 over the subjective methods in matters pertaining to natural sci- 

 1 From The Contemporary Review. 



