162 MR. G. H. HALLIGAN. 



hammering in 88 to 90 feet of water in Sydney Harbour and other places, while its 

 weight — about 10 lbs. to the foot — is not of much moment in borings of less than 

 500 feet depth. When the tube had been lowered to the floor of the lagoon, and a 

 sample of the bottom obtained by the aid of a sand-pinnp, a flexible rubber hose, 

 connected with a 6-in. by 4-in. by 6-in. Worthington steam pump, was attached and 

 water pumped down to scour away the mud, sand, or shells, and thus allow the 

 tube to sink. Additional tubes were of course screwed on as the work progressed, 

 and samples of the strata passed through obtained at intervals, by the tools designed 

 for the purpose. The tools used were of a simple character. lu this, as in all other 

 boring work, success depends more on their intelligent handling than on the tools 

 themselves. 



A boiler pressure of 110 lbs. to the square inch was available, but this was never 

 required ; from 40 to 80 lbs. being the maximum pressure that could be got on 

 the pump cylinders at a depth of 80 feet below the bottom of the lagoon, while 

 at a greater depth not more than from 20 to 40 lbs. could be obtained. The 

 coarseness of the coral gravel at the greater depths does not I think wholly account 

 for this, for during my experience extending over some years I have frequently 

 had to sink through mucli coarser gravel, and have never had any difficulty in 

 obtaining a pressure of from 60 to 80 lbs. on the pump cylinders with similar 

 gear. It would appear as though the ocean had freer access than could be obtained 

 through the coarsest gravel, but this may be explained by the absence from the coral 

 sand and gravel of any mud or fine material, such as is usually foiuid in boiings 

 in river or harbour beds. 



A depth of 1822" feet was reached at 5.35 I'.m. on the day of the starting, the tubes 

 passing for the whole of this distance through Halimeda sand witii more or less 

 fragmentary specimens of shells of marine gastropods and lamelli branch s. Fairly 

 numerous blackened remains of plants were observed at intei'vals in this sand, the 

 last five feet of which was so coherent as to necessitate the yse of an auger in order 

 to penetrate.it. At this depth a hard mass of coral was met with, having a thick- 

 ness of 18 inches, and requiring the use of a heavy steel percussion drill to pierce 

 it. The weight of the tubes was sufficient to enable us, by alternately raising them 

 and letting them fall, to fracture this obstacle, wliich was either a loose slab of coral 

 of immense size or coral rock in situ. Exjaerience generally enables a borer to tell, 

 from the ring of the boring tool, the difference between solid .rock and a boulder, 

 unless the latter is very large. In the present case the ring indicated solid rock, and 

 the occurrence 'of a similar mass at a depth of 193 to 196 feet in the second boring, 

 which will be referred to later on, certainly suggests rock in sit a. 



Below this coral mass we encountered a stratum of coral gravel and sand which 

 extended to a depth of 217 feet. The fragments of this coral gravel varied in size 

 from that of a pear to that of a walnut, pieces as large as a small hen's egg being 

 occasionally met with. They were mostly subaugidar, and quite unlike the well-rolled 



