20 REPORT — 1861. 



As a very nearly analogou8 case, I may turn to the well-known " Septaria " con- 

 cretions, consistinff chiefly of carbonate of u'on or clay iron ore, compressed from 

 without and yielding to pressure, till the outward stratum has assmiied so much of 

 consistency that it will act like an arch or vault against further pressure, while the 

 inside still remains in a softer state, which, however, is afterwards lost by contrac- 

 tion of the main substance, while in the fissures carbonates of lime and magnesia, 

 or even iron pyrites, are deposited. The diagi-am (fig. 5) is taken by stereotype from 

 a specimen in the Imperial Mineralogical Museum of Vienna, 



Fig. 5. 



In the very same manner a solid crust or shell may be the result of pressure from 

 without, on the stratum most distant from the centre, in a lar^e globe of cosmic 

 matter. Pressure will elicit electric action, chemical action will ensue, and heat 

 and light be disengaged, sufficient to form all those combinations and compound 

 rocks, as they come now within our reach in aerolites, or meteoric stones and irons; 

 some of them in the shape of massive rocks of tufaceous structure, others becoming 

 granular in composition, some traversed by veins, others (^and particularly ii-ons) 

 having the character of being the products of veins containing fi-agments or im- 

 bedded crystals, as of olivine or chromite. 



Pressiu-e on the surface depends upon the magnitude of the globe itself: while a 

 portion of matter weighing one pound upon our earth will press upon the smface 

 of it with the effect appertaining to one pound, it will only press with the effect of 

 ■^ths of one pound upon the surface of the moon, but with that of 28^ pounds upon 

 that of the sun. The same pressure which is produced in our planet by a crust of I 

 25 miles, upon the moon vsdll only be produced by a crust of 1621 niUes ; upon the 

 sun by a crust of only ^ths of a mUe, or of only 4656 feet. Heat is then the result 

 of pressure. I may be permitted to quote here a passage fi-om the * Abstracts of the 

 Proceedings of the Geological Society of London,' No. 24, January 5, 1859, in 

 which Prof. Ramsay, communicating a paper by Mr. T. Steny Hunt, states, " The 

 author accepts the views of Babbage and Herschel as to the internal heat of the 

 earth lising through the sti-atified deposits, on account of the superficial accumula- 

 tion of sediments, metamorphosing the rocks submitted to its action, causing eai-th- 

 quakes and volcanic iiTuptions by the evolution of gases and vapours from chemical 

 reactions, and giving rise to disturbances of equilibrium over wide areas of elevation 

 and subsidence." We then have great authorities for the increase of heat by means 



