A SUPPOSED CASE. 87 



or indifference to, the duty of what we may term 

 human communication'? As surely as gravitation 

 is an appointed law of God, so surely is it an 

 appointed duty that men shall communicate their 

 individual knowledge to each other, in order that 

 the general knowledge of the species may advance ; 

 and just in proportion to the fidelity with which 

 men obey this duty the care and ability with which 

 they collate and systematize and investigate their 

 knowledge will be the result of their efforts. 



In order to make the above remarks more clear 

 as regards atmospheric phenomena, let us suppose the 

 case of a sailor who makes the same voyage every 

 year, but not precisely at the same time each year (and 

 it must be remembered that the rigid punctuality at 

 starting which now holds good did not exist in for- 

 mer times). In his first voyage he had to cross, say, 

 four of the wind-belts. While crossing belt number 

 one, he experiences south-west winds chiefly, and, 

 being an observant man, notes the fact. In belt 

 number two he encounters westerly winds. In. 

 number three he is in a region of variable winds 

 and calms. In this region the winds blow all 

 round the compass, averaging about three months 

 from each quarter. But our sailor does not know 

 that ; he does not stay there all the year to make 

 notes ; he passes on, having recorded his experience. 

 In crossing belt number four, he finds the pre- 

 vailing winds to be easterly. 



Next year he sets forth again; but merchants 



