OBSKRVATIONS OF LUMINOUS METEORS. 1G9 



That it has been taken up from tlie atmosphere has been proposed. He finds, 

 however, that tlie iron of the Iowa meteorite contains no more carbonic acid 

 now than it did at tlio time of its fall. 



Leonard gives a detailed account of the appearance presented by the meteor, 

 which is stated to have been seen throughout a region 400 miles from S.W. 

 to N.E., and 250 miles in breadth. The stones vary in weight from a few 

 ounces to 74 lbs., and the aggregate weight is 500 lbs. ; the area over which 

 they were scattered appears to be 7 miles in length, and 4 miles at its greatest 

 breadth. A plan of the townships included in this area is given in Leonard's 

 paper, and it shows where the chief stones fell. By reason' of the frozen 

 condition of the ground at the time of the fall, and the low angle of descent, it 

 appears probable that almost all the fragments which fell have been secured. 

 The velocity of the meteor has not been satisfactorily determined ; it appears 

 probable that during the last 60 or 70 miles of its course it travelled at the 

 rate of from 6 to 7 miles per second. 



An interesting pamphlet by Mr. Irish, C.E., deals with the appearance 

 presented by the meteor. He has incorporated in his paper a number of 

 letters received from observers stationed over a wide ai'ea, describing their 

 impressions as to its altitude, velocity, and appearauco ; and he has given a 

 drawing of the meteor, and prepared a map of the district, showing the pro- 

 jection of its path through the air. I learn by a recent letter from Mr. Irish 

 that two blocks, one weighing 72 lbs., the other 48 lbs., which evidently 

 formed one and the same mass which was disrupted during the descent, have 

 since been found ; and the aggregate weight of the stones now collected cannot 

 be less than 700 lbs. I am also indebted to Mr. Irish for six excellent 

 photographs of the Iowa stones, sixty-seven in number, which form the 

 collections of Prof. Hinrichs, Mr. J. P. Irish, and himself. They were taken 

 by Mr. Thomas James, of Iowa citj', and are in the very best style of photo- 

 graphic art. 



Prof. Giimbel, of Munich, lias recently published an interesting paper oii 

 the characters of this meteorite. He finds the crust to possess a deep bottle- 

 green or brownish-red colour, and to possess in polarized light all the 

 characters of an amorphous glass-like mass. "NYhen a fragment is heated it 

 turns of a dark brown colour, like that noticed by him in the eruptive rocks 

 of the Fichtelgebirg, and he regards this change as a safe indication of the 

 presence of olivine. 



The composition of the stone is found to be : — - 



Meteoric iron 1232 



Troilite .5-2.5 



Silicate, decomposed by acid 48"11 



Silicate, not acted upon by acid 34'32 



10000 



The silicate decomposed by acid is an olivine, having the formula 

 2 (I MgO, iFcO), SiOj ; and the insoluble silicate, which has been regarded 

 by Dr. Lawrence Smith as pyroxene, gave the oxygen ratios — silicic acid 

 = 29-08 ; bases = 10-29. It appears not improbable that in this case the 

 silicate was not completely decomposed during analysis. 



The paper is illustrated with an interesting plate of a microscopic section 

 showing olivine, augite, meteoric iron, chromite, troilite, particles of a reddish 

 hue which resemble garnet but which doubly refract light and exhibit optical 

 characters which will not allow of tbeir being identified with nosean, and 

 chondra showing fibrous, radiate, and granular structure, as well as others 



