LECTURES. 63 



the mind a picture of the air as it is. Some have likened it to a sea, 

 which is true to a certain extent, as the air like the water is constantly 

 moving ; but, on the other hand, no sea has the great mountains and 

 plateaux and valleys which are to be found in the air. If you can 

 imagine a continent as liquid as the sea, yet with massive mountain 

 ranges, and these mountain ranges constantly shifting from one place 

 to another, you will have some conception of the nature of the 

 atmosphere. It is now regarded as certain by some observers both 

 here and in America that there are certain areas of high pressure 

 independent of one another which shift from place to place 

 during certain seasons of the year, that is to say, in summer 

 they leave the land, and in winter approach it. These high 

 pressure systems occur in both hemispheres, but I shall confine my 

 remarks to those of the Northern Hemisphere as the better known. 

 There are five of these systems, one in the North Pacific off the coast 

 of California, one over the United States, one over the Atlantic, one 

 over Central Asia, and one over Greenland. During the Summer the 

 American, Greenland, and Siberian systems disappear, moving away 

 far north where there is prevailing high pressure, and indeed the 

 progress of the Siberian system across Western Russia and Scandin- 

 avia to the N.VV. in spring, returning S.E. in autumn, can be distinctly 

 traced. When the accuracy of these discoveries shall have been 

 firmly established it will remain to discover, if possible, the cyclonic 

 systems, which there is every reason to suppose exist just as much as 

 anticyclonic systems, and which presumably take their course along 

 the lower levels between the high plateaux of the anticyclones, but 

 seeing that neither are stationary, the one may have sufficient force 

 to divert or thrust back the other. Hence arise our storms and other 

 changes and varieties of weather, causing so much trouble and 

 vexation of spirit to the short-sighted man, who, seeing the sun 

 shining in the morning, concludes that it must shine all day, and 

 starting away without any provision for the future is annoyed to find 

 himself drenched or frozen before night. 



My object in reading this paper was to justify the existence of the 

 Meteorologist, at whom many, if not the majority of, people scoff as a 

 kind of Uncle Toby astride his Hobby Horse, which he rides with 

 whip and spur ; but if I have made it clear to you that the apparently 

 meaningless and useless actions and performances of the observer 

 may and do have some practical effect, even though it be in the 

 distant future, and advance the general sum of human knowledge 

 of the atmosphere with which we are surrounded, then my object has 

 been achieved. 



