REPORT OF THE SECRETARY. 41 



was subject to observation was so near the earth as to be controlled 

 almost entirely by its attraction, and not sensibly perturbed by other 

 bodies. The orbit therefore ascertained, is not the path of the meteor in 

 space, but that having the center of the earth in one of its foci. Pro- 

 fessor Coffin proceeded with the data at his command, to determine the 

 path upon the assumption that the earth was a sphere 7,912 miles in 

 diameter, not taking into account its spheroidal form, nor the difference 

 between the f rue and the apparent zenith. In prosecuting the investi- 

 gations, the method adopted was as follows : The parallax and position 

 of the meteor were obtained by combining in pairs observations taken 

 on or near the same vertical plane. Unfortunately, the number of pairs 

 of reliable observations was too few for much accuracy. An approxi- 

 mate orbit was, however, determined, from which azimuths and alti- 

 tudes were deduced, and these compared with those given by the obser- 

 vations. The form of the orbit was then altered so as to diminish the 

 discrepancies, and it was not until over fifty changes of this kind had 

 been made that the final result was attained. The velocity per second, 

 relative to the earth's center, which best corresponded with observations, 

 was nine and three-fourths miles. The first approximate orbit satisfied 

 the most reliable observations west of about longitude 76° or 77° ; but 

 further east the discrepancies were so great that they could be recon- 

 ciled only by a sudden change in the curvature of the path, one at the 

 point just named, and another two or three degrees further east. In the 

 vicinity of the former of these points a remarkable rupture in the body 

 of the meteor was observed, where it separated into two parts that 

 appeared nearly of equal size, thus affording a rational explanation of 

 the change in the elements. That a change should take place at a point 

 of explosion was not difficult to understand, but the fact that the 

 meteor descended quite rapidly towards the earth, until it reached the 

 meridian of 74°, and afterwards rose, was difficult to comprehend. The 

 most plausible explanation was suggested by Professor Lyman, viz: 

 that the change in direction was due to the increased resistance of the 

 air as the meteor descended into a denser portion. An attempt was 

 made to deduce the quantity of the change from this hypothesis ; the 

 result, however, was not entirely satisfactory, an empirical change 

 being assumed in the path near longitude 74°. An orbit was computed, 

 the path of the meteor divided itself into three sections, the first and 

 last of indefinite length, through only a small portion of which the 

 meteor was visible ; the other an intermediate portion of 100 miles in 

 length, where it was most brilliant. The most important omission in 

 the calculation of the elements of this meteor, according to Professor 

 Coffin himself, was that of the spheroidal form of the earth, which be- 

 came of importance in comparison with the small height of the meteor; 

 but with the hope that the subject might hereafter receive at the hands 

 of others a more thorough discussion, he concluded to slightly modify 

 the elements, so as to afford an unperturbed orbit that would differ so 



