INVESTIGATIONS OF THE ALBATROSS. 259 



7:30 a. m. on the 25th a vsoundiug" Avas made in 1,471 fathoms, green ooze. 

 Serial temperatures and specific gravities were taken, and a success- 

 ful haul of the trawl followed, the surface net being towed during the 

 interval of dredging. 



Submarine tow net. — Experiments with a new design of submarine 

 tow net were made later in the day, with unsatisfactory results. In 

 fact, it was a failure, owing, doubtless, to the large size of the net and 

 its small mesTi, which caused undue tension on the bridles while towing". 



The frame is composed of rods and tubing of brass. There is a fine 

 screw-thread on the upper half of the central shaft, which works in a 

 nut in the upper middle part of the frame. The lower end of the shaft 

 is plain and passes through two studs in the frame, which serve as 

 stops for the bridles. A propeller on the middle of the shaft holds it 

 doAvn while the apparatus is being lowered and slowly raises it while 

 the net is towed through the water. The jaws are of two sizes, 3 feet 

 and 2^ feet in diameter, with hinges which i)ermit them to open and 

 shut. The net is 7 feet in length, half-inch mesh, lined with mosquito 

 net for 5 feet, and inside of this lining is another of silk gauze, extending 

 3 feet from the lower end of the net. A weight is attached to the lower 

 end of the net to prevent its floating up and fouling the jaws or bridles. 



To use the apparatus, close the mouth of the net, attach both bridles 

 by their terminal rings to the central shaft and lower to the desired 

 depth, then steam slowly through the water, w^hen the i^ropeller will 

 be brought into action, the central shaft slowly raised, and the first 

 pair of bridles released, opening the jaws. After towing about half a 

 mile the shaft will have reached its upper limit, when the remaining 

 bridle will be released and the net again closed, ready to be hoisted to 

 the surface. This apparatus could be made to act by reducing the 

 size of the net and removing one of the linings, but the chances of acci- 

 dent or irregularity in the working of the propeller were so great that 

 there would always be a doubt as to its having properly performed 

 its functions. Prof. Agassiz was greatly disappointed at its failure, 

 for he considered the examination of intermediate depths among the 

 most important problems to be worked out during the cruise. I had 

 thought little of the matter, as my confidence in the apparatus just 

 described was explicit, but I now set to work to devise something that 

 would do the work. 



The Tanner tow net is designed for the collection of pelagic forms at 

 intermediate depths, and was use<l successfully during the cruise. The 

 net is the same as that previously described, except that the mosquito- 

 net lining is reduced to about half the length of the bag. The upper 

 bridle has four legs attached at equal distances around the ring and 

 shackled to a sinker on tlie end of the steel-wire dredge rope, Avhich 

 serves as a tow-line. The lower bridle has two legs, 10 feet in length, 

 attached to opposite sides of the ring, and a GO-pound sounding shot is 

 toggled on the bight at the lower extremity to act as a sinker. The 



