the Fall of Meteorites on the Earth, 355 



heavier among them found less obstruction in pursuing their way 

 than the lighter ones. 



M. JuKus Schmidt observed at Athens, July 27th, 1859, a 

 magnificent green meteor, moving slowly in twelve seconds 

 through an arc of 28°, commencing with a faint light, and end- 

 ing as faintly, while about the middle of its course it expanded 

 into a ball of 8-10 minutes in diameter, casting an intense 

 light over the whole town and neighbouring hills. 



An orbit having its convexity turned towards the earth's sur- 

 face, as that of the meteor of 20th July, 1860, seen in the United 

 States, may be indicative of a degree of specific gravity inferior 

 to that generally the case in meteorites. In this case the mo- 

 tion of meteorites may become slower and slower, and at last 

 be completely stopped; while there is little chance of their again 

 returning into the cosmical space, from whence they entered our 

 atmosphere. 



The meteorite in question evidently entered the more rarefied 

 strata of the atmosphere, and, perhaps influenced by the short 

 duration of the igneous globe surrounding it, continued on its 

 course into space. Its speed, though somewhat diminished, was 

 certainly not annihilated. 



Hitherto we have left out of consideration the altitude of the 

 atmospheric strata in which a meteor is supposed to move; 

 nor is this omission objectionable : suppose the meteorite moved 

 along close to the surface of the earth under the pressure of a 

 whole atmosphere, answering to a column of mercury 30 inches 

 in height, and at the rate of seven miles per second, it would act 

 on every square foot of resisting air with a pressure of 22 atmo- 

 spheres*; this pressure would only amount to 11 atmospheres 

 at a height of between 18,000 and 19,000 feet, where the baro- 

 meter would indicate an atmospheric pressure of only 15 inches. 

 It must, however, not be lost sight of, that under such circum- 

 stances the resistance of the surrounding air is also notably 

 diminished, and that consequently the atmospheric particles 

 forcibly driven out before the centre of elasticity will find the 

 same facility for streaming along, or flowing in the directions 

 CD, CD' (fig. 1). 



If electric tension in the extremely rarefied strata of our atmo- 

 sphere is really as energetic as it is generally admitted to be, we 

 are entitled to suppose a high development of electrical light. 

 The expressions used by Benzenberg in the above-quoted pas- 

 sage, suggest no idea adequate to our present mode of viewing 

 this subject. The view recently enounced in a totally different 

 direction by one of the first of living physicists, Professor Pliicker, 

 seems to be in exact accordance with the subject considered here. 

 * See E. E. Schmidt's Lehrbuch der Meteorologie, page 913. 



