Thomson. — Portobello Marine Fish- hatchery. 529 



Dangerous brittleness can be guarded against by the impact 

 test. For rails, axles, ordinance, and all moving parts of 

 machines and engines the impact test is of primary importance 

 (it has been calculated that 85 per cent, of the parts of a modern 

 high-speed engine are subject to shock) ; tensional tests must, 

 however, also be made to obtain the data necessary for guarding 

 against the effects of fatigue. 



In conclusion it may be pointed out that no uncertainty 

 need now exist as to the state of a fractured hook, chain, or 

 machine part. A " shock " test will at once make clear whether 

 the piece failed under overload, or was in a .dangerously brittle 

 condition. Further, the condition of existing parts and the rate 

 at which the shock strength of axles, rails, tires, piston-rods, 

 crank-pins, and chains is being used up can be readily ascer- 

 tained, and the parts withdrawn from service before failure, 

 possibly disastrous, ensues. 



The object of this paper being to direct attention to and 

 place in a condensed form some recent developments in the 

 theory of steel, contemporary literature, such as " Harborcl's 

 Steel," and the proceedings of various scientific bodies, has been 

 liberally drawn upon. 



Art. LXI. — The Portobello Marine Fish-hatchery and Bio- 

 logical Station. 



By Geo. M. Thomson, F.L.S. 



[Read before the Otago Institute, loth November, 1905.] 

 Plates LV-LIX. 



I. Historical. 



On the 8th October, 1895, the author, who had previously 

 been in correspondence with Dr. Fulton, Scientific Superin- 

 tendent of the Scotch Fishery Board, on the subject, read a 

 paper before the Otago Institute on " New Zealand Fisheries, 

 and the Desirability of introducing New Species of Sea-fish." 

 In this paper the, possibility of introducing the cod, the her- 

 ring, the turbot, and the edible crab of Britain was considered, 

 and the cost and style of the requisite buildings for a hatchery 

 were outlined. After the subject had been discussed the de- 

 sirability of establishing such a hatchery was affirmed, and 

 a committee, consisting of Messrs. A. Hamilton, J. S. Tennant, 

 and the author, was appointed to report on the best site for 

 the proposed, station. The committee handed in their recom- 

 mendations at a meeting of the Institute held on the 12th May, 



