402 Scientific Geology. 



cause this science teaches that the revolutions of nature have occu- 

 pied immense periods of time, it does not, therefore, teach that they 

 form an eternal series. It only enlarges our conceptions of the Dei- 

 ty ; and when men shall cease to regard geology with jealousy and 

 narrow-minded prejudices, they will find that it opens fields of re- 

 search and contemplation as wide and as grand as astronomy itself. 



UN STRATIFIED ROCKS. 



I have already described several rocks, (ex. gr. limestone, serpen- 

 tine, and one or two varieties of hornblende slate,) as sometimes strat- 

 ified and sometimes unstratified. But the rocks which I include un- 

 der the present division, are never stratified in the proper sense of that 

 term. They are, indeed, sometimes divided into parallel masses j 

 but in such cases this peculiar form seems to result from that kind of 

 crystalline arrangement called the concretionary structure. The 

 question so long agitated, whether these rocks, particularly granite, 

 are stratified, sterns at last to be satisfactorily settled in the negative. 

 This character, therefore, may with propriety be employed to desig- 

 nate one of the great classes of rocks. 



Unstratified rocks occupy but a small part of the surface of any 

 country. In Great Britian Macculloch says they "do not cover a 

 thousandth part of the superficies of the island.'' In Massachusetts 

 however, as may be seen by the map, they form at least a quarter part 

 of the surface. 



These rocks occur in three modes: 1. In irregular protruding 

 masses, intruded in almost every manner among the stratified rocks, 

 and enlarging downwards indefinitely : 2. In the form of veins of va- 

 rious sizes, and often ramified : 3. As overlying masses. It has 

 been stated, also, that they exist interstratified with other rocks : But 

 an examination of all such cases has shown, that such interlaminated 

 masses are always connected with an unstratified mass, and are mere- 

 ly veins, which for a time coincide in direction with the strata. 



One cannot examine the unstratified rocks with attention, without 

 perceiving that their mode of production must have been in some 

 respects different from that of the stratified rocks. Not long since 



