NARRATIVE OF THE SECOND AND THIRD EXPEDITIONS. 45 



least, the return journey having to be made in the teeth of the trade wind. It would, 

 I estimated, have occupied fully a month to erect the staging and the machinery, and 

 under the circumstances I questioned whether we should succeed in doing this 

 satisfactorily at all in the time at our disposal. The cost of boat hire and labour hire 

 too would have amomited to from £40 to £50, which was more than I could afford 

 for the purpose, such small amount of cash as T had being reserved chiefly for dredging 

 and drilling operations on the steep ocean face of the reef. It seemed best under tlie 

 circumstances to try and get a bore clown on the lagoon edge of the reef due west 

 of the diamond-drill bore, with a view of ascertaining the dip, if any, of strata struck 

 iri the main bore.* 



After hard work we succeeded in starting the little drill on the sixteenth day 

 after our arrival. After passing through 7 feet of foraminiferal and Halimeda detritus 

 we encountered a coarse coral shingle for about 2 feet, then a cavernous IJeliopora 

 ccerulea reef-rock with the spaces between the branches partly filled in by a growth 

 of Lithothamnion, a rock which is precisely similar to that penetrated at a similar 

 depth by the diamond drill. The little drill was not intended for boring hard rock, 

 as we had anticipated that the material of the supposed island at the middle of the 

 lagoon would be soft. We tried boring with a bit which we armed with sapphires, 

 but they proved much too brittle for boring the coral rock, splintering quickly along 

 the cleavage planes. We then tried chips of steel files and succeeded in cutting 

 through the coral rock for 16 feet with these, but the file chips sooii had their cutting 

 edges blunted and needed to be constantly replaced, which was laborious and wasted 

 much time. We could, nevertheless, have bored much deeper by this means, if it 

 had not been for (1) The very heavy silt which choked our bore-hole directly the 

 pump stopped working, and (2) We had no under-reamer which would jet water from 

 its under surface concurrently with the work of boring. Our under-reamer was one 

 of the "ball" type, worked on the percussion principle, the favourite type used by 

 artesian well drillers in New South Wales. As soon, however, as we drew up our 

 boring rods and lowered the ball under-reamer to under ream the coral rock, we found 

 that silt had risen in the bore-hole to a height of ten feet or more. We attempted to 

 get rid of this silt with a sand pump, but as often as we withdrew the sand pump 

 from the bore-hole fresh silt flowed in from the tortuous channels at the side. As 

 all attempts to " monkey " our lining pipes through this hard coral rock failed, Ave 

 were forced at last to abandon this small borehole at a depth of 25 feet.t 



The following is the section obtained in the small bore : — Surface of bore about 



* It may be here mentioned that it seems to Mr. Halligan and myself that it would be quite possible 

 and very desirable to put down a bore at Te Akau Tuluaga, but the drilling apparatus, and^staging to carry 

 it, should be of a design different from that which we had with us. Our small drill and staging were 

 built to be used on a sandy islet above the level of high water, and were not suitable for this shoal. 



t It must not be thought that we had come entirely unprepared for boring through silt. The results 

 of the former boring expedition had shown only too plainly that heavy silt was to be expected, especially 



