DREDGING AX OBAN. 83 



twenty minutes at the bottom, beiu<i either towed very slowly by the 

 steamer, or allowed to drift with the current. The rope was hauled in 

 by hand over the side of the vessel in raisinjj the dredf,'e ; but a con- 

 siderable inconvenience was experienced in doiiif^ this, from the labour 

 of the work and the loss of time involved, about nine minutes being 

 generally required for hauling in the dredge, even from the moderate 

 depth of '2'2 fathoms. The provision of some simple hauling winch, 

 with a leading pulley for the rope where passing over the side of the 

 vessel (however rough in construction), will be an important advantage 

 in future dredging operations ; and these should be arranged so as to 

 admit of being readily shifted in position, as the circumstances of the 

 varying position of the dredge in the drifting of the vessel may render 

 desirable. 



A sketch map is appended, showing the localities of the several 

 dredging stations ; and an abstract is added of the log that was kept of 

 the dredging operations, recording in each case the station, the time of 

 lowering the dredge, and the time of remaining at the bottom, with a 

 general note of the contents brought lap, and the nature of the bottom. 



The most important point of experience gained from the dredging, 

 is the great value of the tanrjlef: as a means of securing good specimens; 

 the large Funiculina specimen was brought up by being caught 

 by a few of the hempen fibres of a tangle, and was secured by 

 this means in perfect and uninjured condition ; and one of the 

 two Peuuatula specimens was also caught by a tangle. A serious 

 defect, however, in the present tangles (which are attached one to 

 each bottom corner of the dredge-net), is that the dredge precedes the 

 tangles, and the heavy cutting edge at the mouth of the net conse- 

 quently scrapes over the whole of the ground that is passed afterwards 

 by the tangles, and is thus liable to break off and damage objects that 

 are growing upright at the bottom of the water. An important illus- 

 tration of this damage is given by the circumstance that all the 

 Virgularia specimens (which have a very brittle and rigid stem) were 

 broken off at the bottom, the point of fracture being at a quarter to 

 three-quarters of an inch below the lower extremity of the " feather" 

 or fleshy body, and most probably very near the surface of the ground 

 in which the objects were growing. 



In the report of the "Challenger" Dredging Expedition special 

 value is assigned to the tangles, and as many as eight tangles were used 

 together in the dredging, carried by a transverse bar .5ft. long at the 

 bottom of the dredge-net. which was 4^ ft. wide. A light iron rod was 

 attached to each end of the tangle bar, extending to the mouth of the 

 dredge, as a provision for keeping the dredge-net always extended to 

 its full length, and for preventing any risk of the tangles or the end of 

 the net getting folded over the mouth of the net, and so causing the 

 dredge to come up empty. In the experience of the Oban dredging 

 such accidents occasionally happened, and the adoption of a similar 

 precaution in future is desirable. 



Another point in which the working of the present dredge was not 



