344 THE POPULAR SCIENCE MONTHLY. 



THE METEORITIC HYPOTHESIS. 



By J. ELLAED GOEE, F. E. A. S. 



MUCH has lately been heard about the "meteoritic theory" 

 as an explanation of the origin and construction of the 

 heavenly bodies. This hypothesis, now generally ascribed to Prof. 

 Lockyer, seems to have been first suggested by the German as- 

 tronomer Meyer. His theory has met with some support from 

 Helmholtz, Proctor, Thomson, and Tait in Europe, and from Profs. 

 Newton and Wright in America. Prof. Lockyer has recently 

 published a full exposition of his theory in an elaborate and inter- 

 esting work entitled The Meteoritic Hypothesis : a Statement of 

 the Results of a Spectroscopic Inquiry into the Origin of Cosmical 

 Systems. In this volume the author has worked out his hy- 

 pothesis in great detail, and, as his theory has recently met with 

 much adverse criticism, a brief review of the principal factsa nd 

 arguments advanced by Lockyer, and also by his opponents, may 

 prove of interest both to those who accept and those who reject 

 his views. 



Lockyer commences his work with an account of the falls of 

 meteoric stones recorded in history. The earliest of these dates 

 back so far as 1478 B. c, but, of course, with some uncertainty. 

 Numerous well-attested falls are, however, referred to, and many 

 of these meteorites are preserved in museums, one weighing over 

 three tons being deposited in the British Museum. This fell at 

 Cranbourne, Australia. 



The general form of these meteoric stones is fragmentary, indi- 

 cating that they are the fractured portions of larger masses, burst 

 asunder by the force of the explosion which usually accompanies 

 these interesting phenomena. In the case of the meteorite which 

 fell at Butsura in 1861, pieces picked up at places three or four miles 

 apart could be actually fitted together to form the original mass. 



Meteorites are generally covered by a black crust, clearly 

 caused by the intense heat developed by the mass in rushing 

 through the earth's atmosphere with a planetary velocity. 



Meteorites are generally composed of well-known terrestrial 

 elements. Among these may be mentioned iron, nickel magne- 

 sium, manganese, copper, carbon, sulphur, etc. Some of them, 

 however, contain mineral compounds which are " new to our min- 

 eralogy," such as compounds of sulphur and calcium, sulphur 

 with iron and chromium, etc. Some meteorites contain a large 

 quantity of hydrogen gas, which has been absorbed or "oc- 

 cluded " ; others contain carbonic-acid gas. Some are composed 

 chiefly 'of iron, others mostly of stony matter. 



