IN THE UNITED KINGDOM AND FRANCE. 47 



With respect to the point of the density of the water, it may be 

 stated that at Hayling Island the rate of density which was found 

 favourable to the adherence of the spat was about 27° hydrometer. 



It might be difficult perhaps to lay down any law or exact 

 scale as to the temperature required for a satisfactory spat, but 

 probably when the water ranges from 62° to 72° by day, within 

 those margins, the temperature will be found to be sufficiently 

 favourable. 



It will be noticed in the foregoing report that repetitions some- 

 times occur. These have been found indispensable from the form 

 in which the report has been drawn up, owing to the desire of the 

 Commissioners that each subject should, as far as possible, be made 

 complete in itself, so as to afford clear and definite information. 



Summary. 



In concluding our report we desire to remark that the limited 

 time and resources at our command for investigating a subject of 

 so extensive a character and on which so much difference of 

 opinion exists, has precluded us from giving more than a general 

 account of the state of the oyster fisheries in the different places 

 we visited and the causes which we consider have contributed to 

 their decadence or the reverse. In the instances of artificial cul- 

 ture, whether as regards breeding or fattening, we made as close 

 an investigation as circumstances would permit into the causes 

 which led to success or failure. 



The readiest answer that could be given to the question as 

 to what conditions are most favourable for the production and 

 growth of oysters would be to point to any prolific natural bank, 

 and to detail all the circumstances, so far as ascertainable, con- 

 nected with it as regarded depth, temperature, and density of 

 water, nature of the soil, &c., &c. 



We have, therefore, deemed it of the greatest importance to 

 ascertain as accurately as possible every fact in connexion with 

 natural oyster banks as well as artificial layings, especially in Ire- 

 land. With this object, through the co-operation of the Admiralty, 

 we caused the temperature of the sea to be ascertained simulta- 

 neously at 32 points around the coast of the United Kingdom, direct- 

 ing that care should be taken that this should be done in the prox- 

 imity of natural or artificial oyster fisheries. These investigations 

 were also useful in showing the effect of the Gulf Stream on dif- 

 ferent parts of the coast. 



With a view of determining the soils most favourable to the 

 production and growth of oysters, we obtained specimens of earths 

 forming the bottoms of various fisheries in France, England, and 

 Ireland ; and with respect to the latter country we also obtained 

 some from localities where cultivation had not proved successful, 

 in order to ascertain how far the nature of the ground might have 

 influenced failure. 



In the Appendix will be found a special report on the tempera- 

 ture of the sea by Professor Hennessy, which embodies the results 

 obtained from the voluminous returns of the coast-guard and from 

 France, from which the following conclusions may be drawn : — 



