124 THE VOYAGE OF H.M.S CHALLENGER, 



mile per hour, and on the 13th March, at Station 21, the drag was lowered to 100 

 fathoms, when no movement of the water could be detected. 



Anemometer observations were obtained whenever circumstances were favourable, 

 that is, when the ship was stationary whilst sounding, and the instrument was not 

 masked by an awning, a sail, or any part of the rigging. When first used it was 

 placed on the top of the small deck charthouse on the pilotage bridge ; but as it was in 

 that position so frequently masked by the awnings or rigging, it was shifted to the top of 

 the foremost davit of the weather quarter boat, where it was quite clear of such obstruc- 

 tions. On the 17th February, at Station 2, the force of the wind being registered 

 as 2 in the Meteorological Register, the velocity by the anemometer was 10 miles 

 per hour. On the 21st, at Station 5, the force of the wind being registered as 3, the 

 velocity by the anemometer was 16 miles per hour from noon on that day to 8.40 a.m. 

 on the 22nd. On the 23rd, at Station 6, from 4 to- 6 P.M., the velocity was 30 miles 

 per hour, and the force was registered as 5 to G. On the 24th February, at Station 7, 

 from 3 to 6 p.m., the force of the wind 4 to 5, the velocity was 17 miles per hour. On 

 the 25th February, at Station 8, the force of the wind being 4 to 5, the velocity 

 was 19 miles per hour; and on the 26th February, at Station 9, the force of the wind 

 being registered as 5, its velocity was 23 miles per hour. 



The observations with respect to the position of the ship, wind, currents, temperature, 

 and depth, are represented graphically on Sheets 6 and 7, and Diagram 1. With respect 

 to the Diagrams accompanying this Narrative, they are designed with a view of showing 

 the distribution of temperature in the part of the ocean traversed, and the horizontal 

 and vertical scales have been chosen accordingly. Horizontal lengths or distances from 

 Station to Station are on a scale of 200 miles to the inch, which gives the diagram a 

 convenient length ; and depths are on a scale of 500 fathoms to the inch, which separates 

 the isothermal lines to a convenient distance from each other. Hence, depths or heights, 

 as compared with horizontal distances are exaggerated in a proportion of 400 to 1. In 

 looking, therefore, at the plan as one of the bed of the area, it must be remembered that 

 the inclines as observed were 400 times less steep than they are represented. The diagram 

 shows the isotherms for every five degrees. The positions of the isotherms for each 

 whole degree as represented were found by plotting the observations and drawing the 

 curve as referred to in the preceding chapter 1 (see page 120). 



The dredgings and trawlings in the deeper water of the Mid Atlantic did not yield a 

 large number of animals. An Annelid {Myriochele) was obtained from 2975 fathoms, several 

 Polyzoa and two small Lamellibranchs from 2740 fathoms, and Sponges, Brachiopods, Poly- 

 zoa, small Lamellibranchs, and Gasteropods, and several Crustaceans from 1900 and 1950 

 fathoms. In 450 fathoms, however, close to Sombrero Island, a large number of animals — 

 Alcyonarians, Echinoderms, Annelids, Molluscs, Crustaceans, and Fishes — were obtained. 



1 See Phys. Chem. Chall. Exp., part iii., 1884. 



