328 



SCIENCE. 



movements of individual particles. If the first is true, 

 the same conditions must apply to the transmission of 

 radiant energy, as to the ptopagation of sound. Sound 

 travels through air with a velocity of 330 miles per 

 second, at o° cent. 



Taking for an example a sound produced by a body vi- 

 brating 20,000 times per second and dividing the velocity 

 of sound by this number, we have as the wave length 

 16.5 mm. Clausius has shown that the mean free path 

 of an oxygen molecule is 5000 times its diameter. 



Taking — - — ; mm. as the diameter, we have io 4 

 6 5 x 10' 



mm. as tne mean free path of an oxygen molecule, and 

 dividing the length of the sound wave calculated above, 

 by this number we have 1665 x lQi > or the length of the 

 wave of this extremely high note, is 1665 x io 4 times 

 longer than the mean free path of an oxygen molecule, 

 hence it is evident that the propagation of sound is de- 

 pendent primarily upon the movement of aggregates of 

 molecules. 



The elasticity of the ether is assured to be many times 

 greater than that of the most perfect gas. Assuming 

 that it is 1000 times more elastic than oxygen gas, the 

 average distance between the surfaces of the particles 

 must De 1000 times greater than the average distance 

 between the surfaces of the oxygen molecules. 



Taking as the mean free path of an oxygen molecule, 

 io 4 mm., the distance between the particles of ether 

 would be .1 mm. Now the wave length of a certain ray 

 of red light is .000,609 mm., hence the average distance 

 between the particles is 164 times as great as this particu- 

 lar wave length. It follows from this, that the transmis- 

 sion of radiant energy, through such an elastic medium 

 as the ether, cannot be in any way comparable with the 

 propagation of sound through air. If the energy is not 

 transmitted in this manner, then it must be transmitted 

 in the second way, i. e., by the movements of individual 

 particles. But with an ether as elastic as generally as- 

 sumed, this is impossible, since the average distance be- 

 tween the particles is 164 times as great as the length of 

 a comparatively long undulation, and it would be absurd 

 to say that a vibrating molecule could, by impact with a 

 particle of ether, send the particle 5000 times the diame- 

 ter of the molecule, and further, that the particle would 

 return from this long journey in time for the next vibra- 

 tion. Even assuming that the particles of ether could 

 move fast enough to accomplish this movement in each 

 vibration, then it the molecules are circular, the particle 

 would have to return in a line that was normal to the 

 surface of the molecule at the point of contact, or it 

 would fly off in another direction after impact with the 

 molecule, and as the particles are so far apart, as com- 

 pared with the diameters of the molecules, if one particle 

 was driven off there would be no other to take its place. 

 There would also be required a series of particles in a 

 straight line between the body receiving and the body radi- 

 ating energy. 



But it is needless to enlarge upon this method of trans- 

 mitting radiant energy, for the constant length of undu- 

 lation and undulatory motion itself, would be impossible 

 in a medium, in which the average distance between the 

 particles was 164 times as long as an undulation. 



The only discontinuous medium through which radiant 

 effergy could be transmitted, would be one in which the 

 average distance between the particles was a small frac- 

 tion of an undulation. But in a medium of this sort 

 there would be hardly any chance for compression, much 

 less than in oxygen gas, and to assume that ether is less 

 elastic than a gas, is contrary to the theory ot discontin- 

 uous ether. As a discontinuous ether will not answer the 

 requirements, we must, if we assume any ether, assume a 

 continuous one. By means of a continuous ether all the 

 phenomena of light can be explained. One is inclined, 

 however, to apply to a continuous ether the same reason- 

 ing as is applied to matter. But as ether is not matter, 



we cannot with justice attribute to it any of the proper- 

 ties of matter except extension and elasticity, and till we 

 are much farther advanced in our knowledge of the uni- 

 verse, it will be impossible to say anything about ether, 

 except to assume its existence and its continuity. B. 



THE COMET. 

 The comet was seen from this Observatory at I4h. 30m., 

 June 22, 1881. The latitude of the place is4i° 13'; 

 longitude from Washington in time, 53m. 48s. This 

 longitude is approximate, as we have no transit, and 

 being without a correct astronomical clock, are continu- 

 ally annoyed for want of true time. The latitude is 

 somewhat indeterminate, as the declination circle has no 

 Vernier, reading seconds. The telescope (a fine 6 inch 

 Alvan Clark & Sons), is not precisely in the meridian, 

 and we are unable to place it there with accuracy, hav- 

 ing no micrometer. With all these hindrances, the ad- 

 justment is such that catalogued stars are always in field 

 with power of 60, but in many cases lail to come to the 

 centre or line of collimation. When observation was 

 first made the declination was 43 10', then make <i=the 

 declination = 43 10', and % = the latitude ot New Wind- 

 sor = 41° 13', and take : 



log. tan. 6 = ... 9.972,188 

 log. tan. A = ... 9.942,478 



log. sin. 55 15'= - - 9.914,666 

 which being converted into time = 3I1. 41m. ; and 6h. — 

 3h. 41m. = 2h. 19m., A. M., June 23, mean local time in 

 New Windsor, or time of comet's rising, that is, of the 

 nucleus. The tail being several degrees long and direec- 

 ted towards Polaris, was above the horizon some time 

 before. 



Had the horizon beeu water, the nucleus would have 

 come in sight at 2.19, as it was, an interval of 11m. was 

 required to bring it above undulations of the earth. We 

 thought best not Io telegraph before seeing the nucleus, 

 but as soon as we positively knew the apparition to be a 

 comet, haste was made to send dispatch. The village 

 is on a blanch railroad and telegraph offices are not open 

 nights, so we had to send to the residence of the opera- 

 tor, arouse and engage him to go to the office and send 

 telegram. This took time, and it was not until after 3 

 A. M. that message was sent. Meanwhile we endeavored 

 to place telescope on nucleus but were unable to, as there 

 was a tree in range, causing another delay until 3.30, 

 when observation was made — the nucleus being an hour 

 above horizon and in apparent 



R. A. 5 h - 34m, 



6 43° 10' 



a rough position, as no corrections were made for re- 

 fraction or parallax. 



The telegram read : " Vast comet in northeastern 

 heavens." After mature consideration we regret using 

 so many words, one only — " Comet," — was all that was 

 necessary, when the acute observer, Swift, would have 

 been on the alert at once. Before sunrise we were 

 favored with 30 minutes good definition, when two enve- 

 lopes were seen, the nucleus extending a bridge to the 

 external surface of the inner one. Since, the nucleus has 

 changed form, is no longer round, but has prolonged into 

 a beak-shaped mass, and looks like Comet III., 1862, 

 August 29, as drawn by Challis (Chambers' Astronomy, 

 p. 322). The cometary matter is of great tenuity, as it 

 was seen to run over a sixth magnitude star at ion. June 

 28, which passed about 1 5" from nucleus, yet it was visible 

 through the immense volume of gas. 



The comet was seen from many points in the Western 

 States twenty-four hours before noticed at this place, 

 by steamboat hands, street-car drivers, railroad conduc- 

 tors, night-watchmen, policemen and many others whose 

 business required them to be out all night. 

 New Windsor, III., July tst, 1881. EDGAR L. Larkin. 



