188 DR. G. J. HINDE. 



(81 millims.) ; and from 210-1114^ feet about 2^ inches (58 millims.). The rock 

 cores were very unequal in length, ranging from 1 inch (25 millims.) to 3 feet 

 (900 millims.), and in many instances only imperfect cylinders and nodular fragments 

 were obtained. Each separate cylinder and nodule of core was numbered con- 

 secutively ; from the surface to the depth of 698 feet, reached by the end of the 

 first year's work, the numbers of the cores ran from 1-366 ; on resuming the 

 boring the second year a fresh series of numbering was introduced, and the cores 

 between 698 feet and the bottom of the boring at 11 14^- feet were marked 1a-709a. 



The solid rock cores, however, by no means represent all the material brought up 

 from the boring, for from the surface to a depth of 748 feet, i.e., about two-thirds 

 of the distance passed through, a large proportion of the rock was of so friable and 

 incoherent a character that in the process of boring it broke up into jfine granular 

 particles and powdery material, to which those engaged in the boring applied the 

 general term of " sand."'* This granular material was brought up from the boring 

 by means of the sand-pump, and from samples of it taken at intervals of a few feet, 

 it appears to have been derived for the most part from a porous rubbly limestone, 

 which consisted of foraminifera, small pieces of casts of corals, alcyonarian spicules, 

 echinoid spines and plates, fragments of calcareous algse and the debris of various 

 other organisms with fine sediment. No true oolitic grains were noticed either in 

 the solid cores or loose materials. These fragmentary materials, in some samples from 

 no great depth from the surface, appear to have been but little more than compressed 

 together, but more generally they have been lightly cemented by crystalline calcium 

 carbonate. Their ready disintegration seems to be in great part due to the slight 

 development of the crystalline cementing matrix ; it is probably also connected with 

 the solution or decomposition of the corals which takes place below the depth of 

 200 feet, to which we shall again refer. That the present friable, incoherent condition 

 of the rock which furnishes this fine granular material, depends on other circum- 

 stances than the detached fragmentary character of its constituent organisms is 

 shown by the fact that where the small interstices between the organic fragments 

 are fairly well occupied by crystalline calcite, or, better still, by crystalline dolomite, 

 a very fine, hard, resistant rock is produced. Many of the hardest rock-cores are 

 seen on microscopic examination to consist of foraminifera and other fragmentary 

 organisms thus consolidated. 



The amount of the consolidated rock-cores, as distinct from the fragmentary 

 Incoherent material, is shown in the following list (p. 189). Their aggregate length 

 is 384|^ feet, or an average in round numbers of 1 foot of core in each 3 feet of the 

 boring. 



* This rnateiial differs so greatly from " sand," as generally understood, that so to term it would give 

 an erroneous idea of its real character, and I have therefore avoided the use of the word in referring to 

 this fine material. 



