286 CRUISE OF THE PORPOISE. 



embark them, which was completed on the 19th. The Porpoise then 

 bore away for Tahiti, two hundred and fifty miles distant, which they 

 made on the 21st, and the same day they anchored in Matavai Bay. 



At the time the brig left him. Lieutenant Johnson had succeeded 

 in making a beginning with the apparatus. Considering the novelty 

 of the business, and that all were unacquainted with the uses of the 

 different parts of the machinery, I was aware of the difficulty of the 

 task that would be imposed upon the officer who directed the opera- 

 tion. I had therefore designated Lieutenant Johnson for this business, 

 who, on account of his ingenuity, perseverance, and mechanical con- 

 trivance, was considered by me as most suitable for this duty. The 

 undertaking proved fully as laborious as I had anticipated, and 

 Lieutenant Johnson's exertions were worthy of better success. The 

 principal difficulties he had to encounter were the looseness of the 

 sand, and the falling in of the coral stones. Every means were 

 devised to overcome these impediments, but in the attempts the pipes 

 became choked, broke, and were thrown out of the perpendicular. 

 When the impediments in one place were found to be too great to be 

 overcome, it was abandoned, and the work begun anew. The greatest 

 depth to which he succeeded in reaching was twenty-one feet: ten to 

 eleven feet were generally accomplished without much difficulty ; but 

 after that depth was arrived at, they frequently did not succeed in 

 getting down beyond one foot per day. 



The coral shelf, composed of conglomerates and compact coral rock, 

 seems to liave affiDrded an impediment to further progress. After the 

 breaking of pipes and augers, and the occurrence of various other 

 accidents, principally from the impossibility of maintaining a perpen- 

 dicular. Lieutenant Johnson began from his acquired experience to 

 hope for success, a day or two previous to the arrival of the brig, 

 when the whole was abandoned by order of Lieutenant-Commandant 

 Ringgold, and every thing embarked. I am well satisfied that there 

 is no insuperable difficulty in boring into coral islands ; but in the 

 present case the season of the year was somewhat against them, as 

 it caused them to encounter much more water in the soil than they 

 would otherwise have met with. The proper season for such an 

 attempt would be the dry one. Much rain fell during their stay ; and 

 although no serious sickness occurred, yet many felt unwell. 



To the Geological Report I must leave the details of the boring. 

 Agreeably to my instructions, a specimen of each foot reached was 

 preserved. 



These experiments turned out very much as I anticipated, viz. : 



