THE VOYAGE OF H.M.S. CHALLENGER. 
Station 171a. 
At Toxuatabc 
Station* 172 
axii 172a 
(Toxuatabc) 
6*22 
Station 171a (Sounding 295), New Zealand to Tongatabu (see Chart 27 and 
Diagram 12). 
July 17, 1874 ; lat. 25° 5' S., long. 172° 56' W. 
Temperature of air at noon, 
72 ’3 ; mean for the day, 70° '9. 
Temperature of water : — 
Surface, .... 
72°0 
800 fathoms, . 
37-2 
100 fathoms, 
67 ‘6 
900 „ 
36-9 
200 „ . 
59-2 
1000 „ 
36-7 
300 „ ... 
50-4 
1100 „ 
36-4 
400 „ . . . 
44 0 
1200 „ 
36-2 
500 „ . . . 
41-3 
1300 „ 
36-0 
600 „ ... 
39-2 
Bottom, 
34-3 
700 „ . 
37-9 
Density at 60" F. : — 
Surface, 
1 02642 
400 fathoms, . 
. 1-02576 
100 fathoms, 
1-02635 
Bottom, 
. 1-02626 
200 
1 02646 
Depth, 2900 fathoms; deposit, Red Clay with pumice, containing no carbonate of 
lime (see Murray and Renard, Deep-Sea Deposits Chall. Exp.). 
At 8.30 a.m. got up steam. At 9 a.m. shortened and furled sails, proceeded under 
steam, and sounded in 2900 fathoms. Obtained serial temperatures at intervals of 
100 fathoms down to 1300 fathoms. At 1.20 r.M. completed heaving in line, and at 
1.30 r.M. made sail. At 6 p.m. got up steam, and at 6.30 p.m. proceeded under steam. 
Distance at noon from Eooa Island, 248 miles. Made good 126 miles. Amount of 
current 28 miles, direction S. 52 u E. 
The Challenger arrived at Tongatabu at 9 a.m. on July 19, remaining there till 
8 a.m. on July 22, 1874 (for description of Tongatabu see Narr. Chall. Exp., vol. i. 
pp. 477-486). 
Stations 172 and 172a (Soundings 296 and 297), off Tongatabu (see Chart 28). 
July 22, 1874. 
Temperature of air at noon, 7 1 " *0 : mean for the day, 69°7. 
Temperature of water at surface, 75° - 0. 
At 7 a.m. got up steam. At 7.50 a.m. weighed anchor and proceeded out of Tongatabu 
II irbour, passing between Mallenoah and Attataa Islands. At 10 a.m. stopped and 
