300 OUR SUMMER MIGRANTS. 



observations upon them have reference, as 

 might be supposed, to the dates of their arrival 

 and departure, or, more correctly speaking, to 

 the dates when they were first heard or seen 

 and last observed. When reiferring som^ time 

 previously to the utilization of such observa- 

 tions, it was remarked that upon various poihfs 

 some addition to our knowledge was desirable. 

 Amongst other interesting facts, for exafnple, 

 might be ascertained the precise line of direc- 

 tion in which various species migrate, the causes 

 which necessitate a divergence from this line, 

 the relative proportions in which different 

 species visit us, the causes which influence the 

 ■abundance or scarcity of a species in particular 

 localities, the result of too great a preponder- 

 ance of one species over another, whether 

 beneficial or otherwise to man as a cultivator of 

 the soil, the simultaneity or otherwise of de- 

 parture from this country in autumin, the causes 

 operating to retard such departure, and so forth. 

 All these are matters of interest, especially to 

 those who reside in the country, and have 



