122 MR. E. W. BINNEY ON A MINERAL VEIN 



deposition. Little up to this time has been done to ascer- 

 tain the cause of the union of the particles composing 

 sandstone rocks. It has been attempted, as before stated, 

 to be explained partly by cohesive attraction, and partly by 

 the chemical action of silicate of alumina, silicate of lime, 

 and oxide of iron, in the form of a cement ; but, from the 

 regularity of the divisional and laminated planes, it is now 

 considered that both the latter are in all probability chiefly 

 due to polar forces. 



Dr. Boase, in his treatise on primary geology, at p. 254, 

 cited in p. 281 of Sir H. T. De la Beche's report of the 

 geology of Cornwall and Devon, says, that '' in rocks, as in 

 crystals, the integrant particles are combined and arranged 

 into forms more or less geometrical ; and that, if the rocks 

 do not exhibit such symmetrical figures as perfect crystals, 

 it may be accounted for b)^ their more complicated com- 

 position ; so that their forms are not the simple result of the 

 aggregation of similar particles, but the balance of different 

 powers, each tending to produce a different form.". It is 

 not necessary to suppose that the great divisional planes 

 were all formed at one and the same time, but merely to 

 consider that, during the periods when the rocks were con- 

 solidating, the matter composing them was brought within 

 the influence of forces tending to divide the masses in 

 directions which slightly deviated from each other when 

 viewed on the large scale, though minor modifications may 

 have been produced by the conditions existing during the 

 consolidation of each rock. Mr. R. W. Fox produced 

 lamination in clay by means of long combined voltaic action ; 

 the planes of the laminae being formed at right angles to 

 the electric forces. He considers that the general laminated 

 structure of the clay in his experiments appeared to indicate, 

 " that a series of voltaic poles were produced throughout 

 the clay, the symmetrical arrangement of which had a 

 corresponding effect on the structure of the clay ; and that 



