166 An Improved Grab Crane. 



east Australia, being dry land during the latter part of the 

 Mesozoic period. We have nothing to show us that the 

 lands were connected then, except the present similarity of 

 the fauna and flora, which I hope to deal with at some future 

 time. Let it be well borne in mind, however, that the simi- 

 larity or identity of a fauna and flora is not a proof that 

 the lands were formerly continuous. This similarity may 

 arise from many independent causes, which I need not 

 specify. 



Art. XIII. — An Improved Grab Crane. 

 By C. W. Maclean. 



[Bead 10th August, 1882.] 



The system of dredging by means of a bucket formed of 

 two hinged scoops or forks, known as grabs or clam-shells,, 

 having mechanical contrivances for opening and closing by 

 chains worked by a derrick crane in such a manner as to 

 grapple and lift spoil, has long been known and used by 

 engineers on the Continent. India, Great Britain, America, 

 and other parts of the world. 



Having observed several defects in the working of the 

 usual forms of grab cranes, I designed a new grab and 

 crane which effectually overcomes these defects, and which 

 I will now proceed to describe, prefacing the description by 

 an extract from my British patent specification : — 



" My improvements in grabs relate to the contrivances 

 through which the grappling portion receives its necessary 

 motions of opening, closing, hoisting, and lowering. The 

 improvements in the contrivances used for working the 

 same consist, first, in the substitution of a counterbalance 

 barrel, supported and running in racks at the back of the- 

 crane, for the ordinary counterbalance weight, and in so 

 arranging such counterbalance barrel that it assists instead of 

 retards the engine in all the operations of working the grab ; 



