RECENT HYDROBIOLOGICAL INVESTIGATIONS 491 



surface layers, for the water at depths of 200 metres is no 

 longer affected by solar radiation to an appreciable extent. If 

 the difference between the surface temperature and that at 

 a depth of 200 metres be plotted on the same diagram as the 

 yield of barley, peas, lentils, and beans, it will be found that 

 the similarity of the various curves is remarkably close, 

 particularly for the years 1902 to 1905 ; and the conclusion 

 appears to me to be inevitable that the yield of the land-crops 

 depends on the temperature of the sea and that it should be 

 possible, by making the fullest use of hydrographic data, to 

 estimate some months in advance, with some accuracy, the 

 productivity of the harvests in relation to those of previous 

 years. 



(To be continued) 



