310 ANNUAL OP SCIENTIFIC DISCOVERY. 



let out to that depth it came to a pause. It was then raised a little, 

 and then let out again, when it came to a stop at precisely the same 

 point. The line used was a silk one, one-tenth of an inch in diame- 

 ter, weighing about one pound to every hundred yards, the plummet 

 weighing about nine pounds, and being about eleven inches long. 

 These were perhaps very favorable circumstances ; but there were 

 considerations connected with all deep sea experiments which render- 

 ed these results extremely doubtful, and not only doubtful, but in 

 some cases actually erroneous. This arose from the action of what he 

 had, in a previous paper, spoken of as the strata currents ^ of the 

 ocean, that was, currents flowing beneath each other, in different 

 ways, as he had shown in the case of the Gulf stream and the Polar 

 current. It would be evident that, in the case of a sounding, where 

 as with Capt. Denham, a light lead required nine hours, twenty-four 

 minutes, and forty-five seconds, to run out, the action of these cur- 

 rents would affect the length of line run out, and the sounding could 

 not be relied upon. If the sea were a stationary body, or if its cur- 

 rents were uniform movements of the entire mass of waters from the 

 surface to the bottom, then the lead might be fairly expected to take 

 a direct and perpendicular course downwards. But if, in the place 

 of sounding, strata currents, so prevalent in the sea, should be run- 

 ning in different directions, or what would have the same effect, if 

 one stratum of water, say a superficial stratum, should be in motion, 

 and the main body below at rest, no correct results could be derived. 

 Dr. Scoresby proceeded to show, illustrating his argument with dia- 

 grams, that under such circumstances the line would be carried away 

 by the under current so as to make a bend, which, at great depths, 

 might go to the extent of miles. He had repeatedly noticed this effect 

 when in the Arctic seas, in his youth, hunting the whale, and by 

 noticing it had been able to strike many second harpoons, where the 

 other whale fishers had been at fault. He had noticed that after a 

 fish was struck, say at the edge of the ice, it had dived in 

 an oblique direction under it, carrying out line for a quarter 

 of an hour or twenty minutes, when there would be a tension of from 

 half-a-ton to a ton on the line, and then pause for a short time. Then 

 the fish would " take line " again, as if under the ice, and perhaps 

 come up a-stern of the fast boat. There could be no doubt that the 

 second pulling out was owing almost entirely to the resistance of the 

 water. But if the boat was in clear water, and run until the pause; 

 then her head would perhaps incline to the right or left. The boats 

 then went a-head of her ; but he, instead of doing so, had always 

 gone to perhaps treble the angle of inclination, and had, for the most 

 part, been rewarded by his close proximity to the fish when it rose. 

 Well, then, all circumstances showed that the currents of the sea 

 had very considerable influence on the line when let out, and he 

 came, then to the consideration of a plan for the determination of the 

 surface and relative strata currents. No doubt broad determina- 

 tions as to great and decided currents and proximate results by means 

 of multiplied observations on currents of moderate velocities were 



