﻿10 EQUIPMENT AND WORK OF AN AERO-PHYSICAL OBSERVATORY. 



Observations with high-order nephoscopes would be valuable in throw- 

 ing light on that which is so essential — a knowledge of the true motion 

 of the air. The convectional theory of cyclonic formation, of which 

 Ferrel was the great advocate, has in its favor all that we at present 

 know of cloud motion. But we know so little. The so-called descen- 

 sional theor}^ finds, on the other hand, in the general upper circulation 

 the initiative impulse for storm formation. From this point of view, 

 cyclones and anti-cyclones are but great double vortex knots in the gen- 

 eral air stream. The upper current works down through the anti-cyclone 

 and in a reversed twist out through the cyclone ; and it is evident that 

 cloud motion, had we but the means of observing it properly, would 

 give weighty evidence? Similarly the condensation conditions in free 

 air must be studied. We may get an inkling of the size of the water 

 globules by the colors of cloudy condensation. The Newtonian inter- 

 ference colors might be made use of in some modified form of Michel^ 

 son's " interferential refractometer " to get the dimensions of the condens- 

 ing particles. The increase and decrease of size might be determined 

 and variations interpreted as favoring or not favoring condensations. 

 Every line of research tending to give knowledge of the extent and in- 

 tensity of conditions favoring condensation should be encouraged by 

 weather services. At present the forecaster lacks information worth}^ of 

 acceptance concerning the amount of vapor overhead at different levels ; 

 nor has he any clew whatever as to impending motions of the same, as- 

 censional or descensional. Perhaps the ^question of the production of 

 artificial rain will force meteorologists to develop our knowledge in this 

 direction. Storm motion is to be regarded in the light of a key unlock- 

 ing an appropriately unstable condition of atmosphere. " Dry " storm 

 areas prove beyond doubt that something beside storm mechanism is 

 necessarv for precipitation. The energN^ of a storm and its rate of motion 

 would mean vastly more to the forecaster if he had at his command the 

 seasonal vapor conditions for all elevations. Theoretically the claim of 

 the rain-maker has this much truth to it, that in some districts, at certain 

 times, not only the smoke of a small brush fire, but the unfolding of an 

 umbrella, might suffice to initiate an air motion which would result in 

 more or less precipitation. Furthermore, the forecaster must always 

 clearty distinguish between conditions favoring storm progression and 

 the likelihood of storm formation. Some of the factors operative in 

 storm formation and which the forecaster should be cognizant of are : 

 extent of in-draught of warm moist air and counter-draft of cold dry 

 air ; relative instability of the air ; topography as affecting air drainage, 

 and the vapor values at different elevations. It is ver}^ important that 



