REPORT OF LAGOON BORINGS. 1 (I'J 



pebbles of the present lagoon beach of the atoll. It is absolutely certain that this 

 coral gravel was not formed by the mechanical action of the hydraulic drill, as 

 (l) the fractured surfaces were not recent, but old (2) the gravel was obtained from 

 the bore when the hydraulic jet only was being used ; (3) the gravel rushed in from 

 outside the tubes when they were lifted from time to time, in the endeavour to 

 increase the speed of boring ; and (4) the fragments were much larger than are 

 usually obtained, even when an endeavour is being made to secure large specimens. 



At this depth (217 feet) another coral head or coral block was met with, so hard 

 that it quickly blunted a highly tempered steel drill, and this coral mass also was 

 found to be 18 inches in thickness. It was |)ierced by the drill, but the friction on 

 the tubes at this depth was too great to allow of the obstacle being fractured by the 

 same method as that previously employed, as described above. The driving monkey 

 could not be used, partly on account of the spring of the tube owing to the great 

 depth of water, 101 feet (which with the 15 feet tube above water made a total length 

 of 116 feet of tubing wholly devoid of lateral support), and jjartly because the oscillation 

 of the ship, caused no doubt by her great buoyancy amidships and very fine ends, 

 would not allow of a true blow being struck. It was found that a slight oscillatory 

 movement of the ship was set up by quickly dropping the 5-cwt. monkey at the bow 

 on to the tubes, and this oscillation continued for about 10 or 15 minutes. It is, 

 however, doubtful if any severe driving could be done in 100 feet of water under the 

 most favourable circumstances, the force of the blow being, to a great extent, lost in 

 the spring of the tube. The extreme sensibility of the ship to oscillatory movement 

 was a surprise to me until I had an opportunity on my return to Sydney of examining 

 the sister ship, H.M.S. " Mohawk," in dry dock at Cockatoo Island, when the 

 characteristics of her build, as above noted, at once became apparent. 



It was found impossible to under-ream the hole made through the coral struck at 

 the 217 feet level, as the sand and gravel entered the tube immediately it was raised 

 sufficiently high to allow of the under-reamer being used. The tubes could not, 

 therefore, be driven or lowered below this level, and it remained to us to sink by 

 augurs and drills until the friction caused by the falling in of the material passed 

 through prevented further progress. This we did, and obtained a depth of 245 feet 

 below low-water spring tides, still in coral gravel and sand throughout, as the 

 specimens will show. 



It was now the 19th of August, and as the Admiralty arrangements would not 

 admit of the ship staying beyond the 23rd, there was not time to weigh anchor and 

 move the ship to another position, so I abandoned the idea of a second bore. At the 

 suggestion, however, of Captain Sturdee, the starboard anchor chain was eased out, 

 almost to its full extent, and the port and stern lines hauled taut, thus mooring the 

 ship about 90 feet northward, and a fresh bore was started in the hope of getting clear 

 of the coral heads or boulders. 



I found it impossible to draw the tubes from bore No. 1, as the oscillation of the 



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