150 NATUKALIST'S DREDGE. 



and which can only be had by ordering it specially of 

 a blacksmith. This kind was first recommended many 

 years ago by Robert Ball, LL.D., the well-known zoolo- 

 gist, and its value has been largely tested, especially 

 in deep-sea dredging. It is an iron rectangukr frame, 

 made with a scraper at each side, and having a bag 

 attached to it in the usual manner. Its handles are 

 movable, being connected by eyelet holes with the bars 

 of the frame below, and united, where they join above, 

 by a ring and screw, so that when you wish to pack up 

 the dredge, the handles, on the ring being unscrewed, 

 fold up, and the whole fits into a small compass. This 

 compactness is one advantage of this kind of dredge, as 

 it renders it much more easy of carriage. But its great 

 value lies in the double scraper, which makes it a mat- 

 ter of no consequence on which side the instrument is 

 thrown down. It cannot be reversed. The top and 

 bottom being alike, it is a matter of indifference which 

 shall scrape the ground. In working with a common 

 dredge, if the instrument be not carefully thrown down 

 it is very liable to overset, and unless it fall with the 

 scraper in the proper position, it will not collect any- 

 thing. The Naturalist's Dredge cannot overset, because 

 either side scrapes equally well. And this, when dredg- 

 ing in deep water, is a quality of the greatest value.* 



* Since the publication of the previous edition of this volume 

 Dr. Ball has improved the construction of his dredge, by shortening 

 the handles to the length of the frame, and substituting for the parts 

 cut off, chains, which are connected by a plain ring. This change 

 obviates the necessity of unscrewing the ring when you wish to pack 

 up the dredge, which is therefore always ready for work at a mo- 



