TIDES. (33 



moon is greater than that of the sun, the effect is 

 always to separate the two daily tides, if the luminaries 

 are upon the same side of the equator; but if they be 

 upon different sides, or if the declination of the moon 

 be less than that of the sun, the tendency is to bring 

 the two tides nearer to the same parallel, and thereby 

 to increase the general effect. Such are the operations 

 of gravitation, without reference to the action of heat 

 upon the atmosphere, or the surface of the earth, which 

 affect the seasons, and are on that account necessary 

 to be known before the natural history of the year can 

 be fully understood. Indeed, the details of them are 

 so complicated and so difficult to be understood, that, 

 in the present state of our knowledge, they rather 

 point out where the difficulties lie, than how they are 

 to be got rid of. Still, however, the knowledge of 

 them is valuable in so far as it points out where our 

 observation and inquiry should be directed, and as 

 showing that, for all the labourers that have done good 

 and even harm in it, the field of nature instead of 

 being exhausted, is yet unknown in very many of 

 those every-day matters, the full understanding of 

 which would be fraught with the most important 

 practical effects. 



But the most important of all the seasonal actions is 

 the distribution of heat, immediately from the sun, but 

 wonderfully modified, by the atmosphere through which 

 it passes and the nature of the substance or surface 

 upon which it falls. Heat may be in part regarded as 

 the active principle of nature ; not only as that which 

 counteracts gravitation, but as that upon which the 

 bulk and consistency, as well as the formation and 



