PROCEEDINGS OF SOCIETIES. 67 



the abundance of tangles or sea-weeds of the genus Laminaria which flourish 

 in it around the shores of Europe. On sandy ground these are replaced by the 

 grass-wrack or Zostera. Vegetable-feeding shell-fish and naked mollusca are 

 exceedingly numerous in this space. Its usual vertical extent may be stated to be 

 between low-water mark and fifteen fathoms (90 feet). Owing to the depth of the 

 Laminarian Zone, no mollusca can be obtained from it except by dredging ; and 

 here, for the sake of those who are not quite masters of this subject, I may add a 

 few words about the dredge itself, and of how and where to use it. 



There are several kinds of dredges, but the one that is now universally used 

 is called the naturalist's dredge, first recommended, many years since, by Dr. Ball. 

 It consists of an iron, rectangular frame (if the iron be galvanized it will resist 

 the action of the sea-water better) 13 inches by 3 will make a convenient- sized 

 dredge ; but, of course, it can be made of any size ; a scraper is attached to each 

 side, having a bag attached in the usual manner. This bag can be made of spun 

 yarn, or of fishing-line, netted with a small mesh, or, what is best of all, when it 

 can be obtained, raw hide, cut into fine thongs, and netted in like manner. The 

 meshes might be three-fourths of an inch at the iron rim, and diminish to one- 

 fourth at the end of the bag; but there should always be a free current of water through 

 it while the dredge is on the bottom, or else it only acts as a scraper, driving every 

 thing before it and coming up empty. The handles of the dredge are moveable, 

 and are nearly the length of the frame, so as that they may both lie evenly in the 



rce between the scrapers of the dredge ; to each of the handles is attached half a 

 en links of a chain, which are connected by a plain ring, to which the rope is 

 attached ; the flexibility of the chain increases the biting power of the scraper. 



The dredge may be thrown out of either the stern or side of the boat; and it will 

 economize time, if to the same rope two dredges be attached ; so that while one is 

 examining the contents of one dredge, the other may be actively employed of course, 

 as you pull up the one you let down the other ; you should allow nearly thrice as 

 much rope to be overboard, as the perpendicular depth would require ; thus, if you 

 were dredging in seven fathoms of water, you should, at least, have, over- 

 board, twenty-one fathoms of rope, otherwise your dredge will only hop along the 

 bottom. In case the dredge gets fast in a rock, or in a large Laminarian forest, it 

 is advisable to reverse the rowing, so as to pull contrariwise to that in which the 

 dredge has been entangled, and this will generally succeed in getting it free. In 

 dredging in sounds, or where currents prevail, in a row-boat, of course, you 

 always row with the current ; and in sailing, the boat is put before the wind the 

 inward edge of the rope, in all cases, being made fast to one of the boat's thwarts ; 

 but this should be done with great caution ; for if the dredge gets suddenly 

 entangled, and the rope that connects it be good, it will be very likely to carry away the 

 mast, if not upset the boat. This accident has happened in dredging in the west 

 of Ireland. For deep-sea dredging, where there is danger of the dredge floating, 

 this difficulty can be removed by affixing a weight at a short distance from its mouth. 



It is not on every coast that dredging can be practised. On some, the surf is 

 habitually too great to admit of boating. On some shores no boats are to be had, 

 there being no harbours where they can be kept in safety. On the west coasts of 

 Ireland, for example, the broad waves of the Atlantic continually rolling in, keep 

 up a troubled water, in which the pursuits of the deep-sea naturalists can rarely be 

 carried on. In other places, a rocky, or, as it is technically called, a foul bottom, 

 and, in other terms, fields of sea-weeds, marine forests, present insuperable 

 obstacles to the use of a dredge. Land-locked bays and harbours, where a quiet 

 water flows over a smooth or a shingly bottom, or lies on oyster or scallop beds, 

 are the favourite grounds for the amateur dredger not that but sometimes he will 

 even face the roar of the Atlantic in the cause of science. Where large banks 

 occur at a long distance from land, they greatly reward the naturalist ; but require 

 an absence from the shore of several days. The naturalist will frequently find, 

 thrown up on the Littoral Zone, large heaps of dead shells, the proper inhabitants, 

 when living, of the Laminarian or, perhaps, more frequently those of the Coralline 

 Zones ; by paying accurate attention to the currents which set in and about the 

 heap, he will be able, in general, to trace the locality of the living shells, which 

 will be mostly found in beds. 



