102 



ATMOSPHERE. 



vation. (Amer. Jour, of Science, September, 

 1865.) 



Secchi has calculated the heights of a large 

 number of meteors observed, if appears, August 

 5th to 10th (inclusive), 1864. Bis base-line is 

 that joining Rome and Civita Yecchia, a dis- 

 tance of 65 kilometres (the kilometre = 1093.64 

 yards, nearly), and the two stations being elec- 

 trically connected. The following table gives 

 the estimated heights of 56 of these meteors: 



Height. Number. 

 40 to 60 kilometres 6 



60 



80 " 100 

 100 " 120 

 120 " 140 

 140 " 160 

 160 " 180 

 180 " 200 

 200 " 220 

 220 and higher, 



Total, 



7 

 10 

 IT 

 3 

 5 

 2 

 1 



56 



Thus, 27 of these meteors nearly one-half 

 were observed at heights varying from 80 to 

 120 kilometres (about 49.7 to 74.55 miles). Of 

 93 meteors in all, for which calculations were 

 made, the mean height at first appearance comes 

 out in round numbers 100 kilometres (about 

 62.18 miles), the mean height of 69 of them 

 being 101 kil^m. Fourteen others, moving in 

 the plane passing through the two observatories, 

 made their appearance at a height of about 93 

 kilom. The greatest height observed was 260 

 kilom. (about 161.68 miles); and many were 

 certainly above 200 kilom., with an error at 

 most of 30. The height of the point of extinc- 

 tion was about 75 kilom. (46.635 miles, nearly). 

 M. Faye, however, in stating that the phenom- 

 ena of shooting stars, fire-balls, and meteoric 

 stones have rectified our ideas of the extent of 

 the terrestrial atmosphere, goes beyond all the 

 authorities thus far quoted, and declares that, 

 judging from the phenomena named, the gase- 

 ous envelope of our plane"t should stretch to a 

 height of 240 or even 300 miles. 



Now, that an atmosphere which has been 

 shown by repeated and careful observations to 

 be reduced at a height of about 2f, or at most 

 of 3J miles above the sea-level, .to a density 

 only half that which it has at such level, should 

 nevertheless extend to heights of more than 

 200 nay, even so far as 100 miles above the 

 earth's surface, appears' quite impossible. And 

 yet, either the determinations of the heights of 

 meteors are radically at fault, or else some ma- 

 terial medium, and more dense than any occu- 

 pying the inter-planetary spaces at large, does 

 encompass the earth to depths as great as those 

 above indicated. Here are apparently contra- 

 dictory facts, which science cannot as yet rec- 

 oncile, but to all of which it must seek to af- 

 ford^the correct solution. What is this material 

 medium existing at 100 or more miles above the 

 earth, but certainly terminating at some height 

 above that? If it be some extremely rare min- 

 eral or nebular vapor, such as (ia somewhat 

 different forms) Biot and De la Rive have, in 

 explanation of auroral phenomena, imagined to 



exist in the inter-planetary spaces, and if at 100 

 miles or more beyond the earth's surface this is 

 so far dense as to heat previously dark meteoric 

 bodies to whiteness by its resistance, why is 

 this mineral vapor not still more condensed near 

 the earth, and to such quantity as readily to be 

 detected in the air by chemical examination ? 



Although not offered as answering these 

 questions, it is at least interesting to note that 

 Dr. Reichenbach, of Vienna, led by the phe- 

 nomena of aerolites to the theory that space 

 generally is filled with a cosmical dust, which 

 he supposes may sometimes become agglomer- 

 ated, and sometimes reach the earth as an im- 

 palpable powder, has collected dust from the 

 top of a high mountain, where no tools had 

 ever been used, and having analyzed this, states 

 that he finds it to contain almost identically the 

 same elements as those of which meteoric stones 

 are composed, and among which he names ni- 

 trogen, cobalt, iron, and phosphorus. He thinks 

 such an invisible rain may be [in part] the source 

 of phosphorus in soils, and so [to all higher 

 vegetation] as necessary as aqueous rain. 

 (Quart. Jour, of Science, January, 1865.) It 

 has been suggested that the dust found by 

 Reichenbach was probably blown by winds to 

 the places where it was met with. The pecu- 

 liar composition of the dust, such as few soils 

 or rocks, if any, would be likely to yield, is an 

 objection to this supposition. If the elements 

 contained in it are found oxidized or otherwise 

 combined, may not the dust be regarded as so 

 much of the ashes of consumed meteors? Mr. 

 II. A. Newton has, in a paper read before the 

 National Academy of Sciences, August, 1864, 

 but of which an abstract would not here be in 

 place, estimated the number of meteors the 

 telescopic included which daily enter our 

 atmosphere, as not less than four hundred 

 millions I Be they more or fewer, their ashes 

 must, to some extent, pervade portions of the 

 atmosphere, and it would appear also, reach 

 the earth. But if the elements above named 

 were in part found unoxidized, then, is it 

 not at least supposable that under the con- 

 ditions attending the combustion of meteoric 

 bodies, this process may be to some extent di- 

 rectly attendedby one of dissociation [see CHEM- 

 ISTEY, Ann. Cyc., 1863 and '65] : so that, of the 

 matter of consumed meteors, more or less might 

 still refcch the earth in the elementary condi- 

 tion? At all events, it is certainly probable 

 that soils on the arth are slowly but continu- 

 ally fertilized by meteoric contribution from 

 planetary space ; but it may bo regarded as al- 

 ready reduced to a certainty that from the 

 same source the earth itself is continually gain- 

 ing minute accessions in volume and weight. 



In regard to the temperature of the atmos- 

 phere at different elevations, Mr. Glaisher's ob- 

 servations confirm the view of Leslie, while 

 giving more definite results [see BAROMETER], 

 in showing a more rapid decrease of temper- 

 ature with ascent near the earth than at greater 

 altitudes. The balloon ascents thus far report- 



