108 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



lows these first spiral carvings, because in their directions 

 the air finds the least opposition to its movement. There 

 can scarcely be any doubt that, in the main, these words of 

 Reye express the exact nature of the currents of air, as, indeed, 

 was long ago mathematically demonstrated by Mr. Ferrel, of 

 Cambridge. In explaining the structure of water-spouts, 

 Reye maintains that in this case we have in the interior of 

 the spout a vertical current of air carrying up the warm and 

 moist air, while from above may possibly flow downward 

 colder air. The suddenness with which the water-sj^outs are 

 formed in a quiet atmosphere suggests that they must be 

 preceded by an unstable equilibrium of the air, and that, by 

 means of this, a powerful interchange of the strata of air 

 must take place, by which at once the stable equilibrium is 

 brought about. The question under what condition of tem- 

 perature quiet air can exist in stable equilibrium, Reye an- 

 swers by a computation, showing that this takes place Avhen 

 the temperature of the air decreases by one degree Centigrade 

 or more for every one hundred meters of elevation. He also 

 demonstrates that moist air rises in the atmosphere much 

 more easily than dry air, since the former rises when the 

 diminution of temperature for one hundred meters amounts 

 to one third of a degree Centigrade. With reference to the 

 progressive motion of cyclones, Reye's theory sheds some 

 light, in that it shows that these must always move toward 

 that side on which for a lonor time the warmest and moistest 

 air has been rising, on which the thickest clouds have been 

 formed and the most rain has been falling. This agrees com- 

 pletely with observation and the principles announced inde- 

 pendently in 1870 by Mohn, and in 1871 by Abbe. With re- 

 gard to the parabolic form of the paths of the centres of 

 storms, he inclines to think that it is determined by the form 

 of the Avarm currents in the seas over which the cyclones 

 move. 7 (7, 1873, 314. 



BARBADOES EAIN-FALL AND SUGAR CROP. 



Governor Rawson, of Barbadoes, has just published the 

 text of a work on the rain-fall of that island, and an in- 

 vestigation of the connection between the rain-fall and the 

 crops, especially the sugar crop, which is the staple pro- 

 duction of Barbadoes. This investigation is quite unique 



