184 Bibliography. 



Dr. Jackson has furnished a lucid account of the minerals that are 

 essential to the constitution of rocks. He remarks that silex, the 

 most abundant substance in the globe, enters into the composition of 

 all plants, and Prof. Liebig, in his recent work on the Chemistry of 

 Agriculture, has shown that the silex is always taken up by plants in 

 the form of silicate of potash ; for, the decomposition of the primary 

 rocks to form the basis of our soils, furnishes both materials in abun- 

 dance, Silex is also, in vast quantities, the petrifying material of my- 

 riads of animalcules* beneath peat bogs and in marshes and swamps. 



The fixed alkalies, potash and soda, found in the proportion of 10 

 to 17 per cent, in the feldspar of granite, have not yet been extrica- 

 ted from the feldspar by any process for the use of the arts, but they 

 are constantly evolved by the natural decomposition of the mineral, 

 probably in a great measure by the action of the carbonic acid of the 

 atmosphere and by the vegetable acids. 



The granular quartz or firestone of Woonsocket, a member of the 

 mica slate formation, is used by all furnaces in the Atlantic States. 

 The mica fuses, and thus agglutinates the grains more firmly together. 



Dr. Jackson is decidedly of opinion that the hornblende rock is of 

 igneous origin ; it sometimes passes into serpentine, and is associated 

 with soapstone and magnesian carbonate of lime, (dolomite,) whose 

 origin it is supposed may be from the transfer of magnesia from the 

 hornblende rock to the limestone, "by some unknown chemical pro- 

 cess," in accordance with the theory of Von Buch. Is not this a case 

 where the proposed explanation presents a greater difliculty than the 

 one it proposes to solve ? " Hornblende rocks yield by their decom- 

 position an admirable soil, warm and of good texture." 



The magnesian limes of Rhode Island are much esteemed " for the 

 quickness of their setting when converted into mortar, as also for the 

 beautiful whiteness of the lime." Hence the lime made from the Smith- 

 field " hard jointer" rock, commands a higher price than any other. 



In Rhode Island, the transition slates, instead of being filled, as is 

 usual elsewhere, " with fossil trilobites and marine shells, contain an 

 immense number and variety of cryptogamous and cellular plants," 

 the usual attendants of coal strata ; " and in this deposit occur all the 

 beds of anthracite of Rhode Island and Massachusetts." 



"At the junction of the slates and granite rocks, various remarka- 

 ble metamorphoses are seen, and the clay slate is either cemented into 

 mica slate, flinty slate, or even scoriae filled with epidote, as may be 

 seen on Newport Neck." 



Dr. Jackson is of the opinion that both on the eastern and western 

 continents, a great deluge of waters has rushed from the north south- 



* Or Conferva, see notice in this No, p. 174. 



