The Science of the Weather 707 



meteorological stations, on account of its expedition, for it is 

 quite possible to have all the results worked out by the time the 

 flight has ended. 



Observing the Tracks of the Balloons 



The balloons follow curious tracks at times, especially at 

 stations on our eastern coasts, when a sea-breeze may be blowing 

 shorewards, for the balloon in such a case will travel westwards 

 over the land, but as it is rising at the same time it will soon 

 pass beyond the influence of the easterly breeze, and, if the wind 

 above is from some westerly point, as is usually the case, the 

 balloon will often return overhead across the station and be lost 

 to sight far over the sea. At other times the track will form a 

 wide sweeping arc, generally tending towards the right; occa- 

 sionally the track will be a somewhat irregular spiral; in fact, it 

 is the exception for the track to be a straight one. This means, 

 of course, that the wind directions at various levels in the upper 

 air are often very different from those at the surface, and this 

 fact is of the utmost importance to aerial transport, for an air- 

 craft can at times reach its destination more quickly by choosing 

 a suitable level. 



Astonishing Facts Revealed 



Small as they are, these pilot balloons are often kept in view 

 to very great heights; it is quite common for 20,000 feet (nearly 

 4 miles) to be reached, and half as much again has been exceeded, 

 ere they have been lost to sight in the theodolite telescope. The 

 larger registering balloons have reached even greater heights, for 

 records have been obtained of the temperature and pressure up 

 to fourteen miles above the earth's surface! And these records 

 have a very curious story to tell us. In days gone by it was 

 always believed that the higher we ascended the colder it would 

 become until the cold of outer space was finally reached. But 

 this is not so; the temperature does fall off with height until a 

 certain level is reached, but above this level the temperature 



