MR. W. H. DINES ON VERTICAL TEMPERATURE DISTRIBUTION. 



or 



must continue up to the height at which the isobaric surfaces suv level planes, 

 rather spheroids concentric with the earth. It will be seen from the diagrams that 

 this point lies at a height of about 20 km., and the numlier and consistency of the 

 observations is sufficient to make this fairly certain. The slope of the isobaric surface 

 reaches the same value that it has at the earth's surface at about 16 km., and if we 

 denote this by 1, it reaches its maximum value 1'5 at about 10 km. Our knowledge 

 of the wind above the level of the highest clouds is very limited. It is true that 

 balloons have been followed by a theodolite up to 16 km. or more. Mr. CAVK, who is 

 an authority on this point, considers that the wind falls oft' as the isothermal region is 

 reached, but on some occasions a strong wind is found at 15 km. ; there are four such 

 instances on record at Pyrton Hill. But the balloons can only be followed to great 

 heights when the air is clear and the lower winds light. If the lower winds are 

 strong, the balloon is too far off to be visible long before it has reached the 

 isothermal region. 



On many occasions there is no great wind up to at least 20 km., so that the 

 supposed strong westerly winds, if they exist at all, are intermittent, and different 

 in character to the N.E. and S.E. trade winds. 



The fact that from a station in England many quite likely tracks for a balloon end 

 in the sea introduces a large systematic error, so that no just conclusions can be 

 drawn from registering balloons in England as to the prevalence of certain winds. 

 In most cases the track runs parallel, or nearly so, to the surface isobars, so that 

 generally the direction of the upper wind does not greatly differ from that of the 

 lower, and since also very high ascents do not show longer runs than those of average 

 height, it is certain that the wind velocity decreases rather than increases above 1 or 

 12 km. But there is nothing in the observational results to negative the supposition 

 that strong winds may on some occasions exist at a height of 15 km. A persistent 

 current of this kind in the general circulation would be easily explained, but it is 

 hard to see in the case of intermittent winds whence the energy can come and where 

 it can go. Also cyclones cannot be caused solely by the upper winds, for if so they 

 would have no reason to avoid continental areas, and prefer moist areas, such as the 

 sea or the chain of the Great Lakes of North America, as they undoubtedly do. 



