120 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



humidity at different times of the day, but rather in the in- 

 ertia of the atmosphere, which in the morning permits its 

 elastic force to be increased by a rapidly increasing tempera- 

 ture before its inertia of rest can be overcome sufficiently 

 to allow it to enlarge its volume ; but when that inertia of 

 rest is overcome, then the inertia of motion permits it to re- 

 move from the place of observation any excess of what is due 

 to the increased elasticity. The nocturnal maximum and 

 minimum are caused, then, by the resilient power of the air, 

 which gives it alternately an inward and outward motion, 

 and each way in excess of what is due to the decrease or in- 

 crease of elasticity by reason of the inertia of motion. If 

 this explanation is correct, we ought to find a certain tend- 

 ency of the wind toward east in the morning and toward 

 west in the evening; and this tendency does seem to be 

 shown in the very few published observations which permit 

 a comparison to be made. Further observations, as confirm- 

 ing or disproving the proposed theory, are much to be de- 

 sired. 12 A, 1874, IX., 495. 



PROTECTING INFLUENCE OF THE EARTH'S ATMOSPHERE. 



Weilemann, after reducing the hourly observations made at 

 Berne, Switzerland, for seven years, and deducing therefrom 

 the laws of diurnal change of temperature, has investigated 

 the influence of cloudiness on the daily variation, especially 

 at night. He finds that the radiating power of the earth's 

 surface is every where and at all times the same. The tem- 

 perature in the morning is, he finds, in cloudy weather five 

 or six decrees higher than in clear weather. And, again, 

 the simple atmosphere of the earth surrounds it like a pro- 

 tecting layer of clouds, and that without this the earth 

 would experience daily an enormous variation in tempera- 

 ture. Even the clear sky, or rather the moisture present as 

 an invisible vapor, protects the earth, with an efficiency equal 

 to about one third of that exerted by a layer of clouds, against 

 too strong a daily change of temperature. 19 (7, 1874, 194. 



THE EECENT MAURITIUS HURRICANE. 



Severe hurricanes have of late attracted so much attention 

 that they have ceased to be novelties, and it would hardly 

 be worth while to mention a special one that lately occurred 



