Dr. Walter Flight— On Meteorites. 67 



detected. These researches have led the author to accept the follow- 

 ing conclusions : — 



1. The stony meteorites are distinguished from those which are 

 metallic by occluding the oxides of carbon, chiefly carbonic acid, as 

 their characteristic gases, in place of hydrogen. 



2. The proportion of carbonic acid evolved is much greater at low 

 than at high temperatures, and is sufficient to mask the hydrogen in 

 the spectrum. 



3. The amount of gas contained in a large meteorite, or a cluster 

 of such bodies serving as a cometary nucleus, is sufficient to form 

 the train as ordinarily observed. 



4. The spectrum of these gases closely resembles that of several 

 of the comets. 



The emission of gaseous constituents by the action of solar heat 

 may explain the loss of tail and the diminution of brilliancy observed 

 in the case of several comets in their successive revolutions ; and 

 their final disappearance from sight will follow as an inevitable 

 consequence, the number of revolutions necessary to discharge the 

 gases depending chiefly on their size and the nearness of their 

 approach to the sun at their perihelia. When a meteorite enters our 

 atmosphere, the gases which are evolved from it by the heat which 

 is liberated must greatly contribute to increase the intensity of that 

 heat, while the sudden expansion which these gases experience must 

 constitute the leading cause of the violent disruption of these masses. 



The conclusions arrived at by Wright, on examining the gases 

 occluded by the iron of these meteorites, have been referred to. He 

 considered that the stony meteorites were distinguished from the 

 iron ones by having the oxides of carbon, chiefly the dioxide, as 

 their characteristic gases instead of hydrogen. This theory has 

 been called in question by Mallet, who refers to his examination of 

 the gases of the iron of Augusta Co., Virginia, where the ratio of 

 the oxides of carbon to hydrogen is 4 : 3, and to his having pointed 

 out in 1872 that hydrogen could no longer be regarded as the 

 characteristic gaseous ingredient of meteoric iron. In his paper of 

 that date he stated that although it might be assumed that carbonic 

 oxide would be the original form in which the gaseous carbon- 

 compounds existed in the iron, and that it broke up at the temperature 

 of the experiment into carbon retained by the iron and into carbonic 

 acid, yet in view of the steady decrease of the quantity of the latter 

 gas which was evolved as the experiment proceeded, it seems more 

 likely that a larger amount of carbon originally existed in the 

 higher state of oxidation. Mallet considers that, when all the cir- 

 cumstances of the experiment are considered in each case, Wright's 

 conclusion cannot be sustained. 



In a paper dated some months later, Wright replies to Mallet's 

 criticism. He states that he only meant this expression of opinion 

 to be tentative, but that the results of further work completely 

 justify the conclusion at which he had arrived. He has re-examined 

 the gases of the iron of this meteorite, and examined those of the 

 iron of some other stony meteorites, such as Ohio, Pultusk, Parnallee, 



