PHYSICS OF THE GLOBE. 71 



frost, the temperature of surrounding air rises to 32 Fahr., 

 and even above, while higher up the strata of air continue 

 to be even below 32. The isothermal surfaces near the earth 

 during the night are not always horizontal or parallel. 



Hellmann, in a memoir on the variability of the tempera- 

 ture in Northern Germany, gives many comparisons of local 

 interest, especially relative to the influence of the Baltic and 

 North Sea. 



In an important memoir on the annual temperature pe- 

 riod, Kascona first deals with the theoretical formula?, and 

 then applies them to observations at Modena,Bologna,Milan, 

 and Geneva. He shows that the radiation of heat at night 

 from the earth is proportional to the solar radiation re- 

 ceived during the day. Among the many very interesting 

 results of his investigation, he gives formulae representing 

 the annual changes in the daily maximum and minimum 

 temperatures, and shows that the mean of these two formu- 

 lae represents the mean annual temperature. 



WINDS AND CURRENTS. 



Anything that draws the attention of observers to the im- 

 portance of observing the actual heights and movements of 

 the clouds is to be welcomed, and we note, therefore, the 

 little work of A. Ringwood, of Australia, in which he gives 

 some methods, but by no means exhausts the subject. The 

 methods that have been proposed and used are now so nu- 

 merous and various that any one who will may easily make 

 these important measurements. Among these is one pro- 

 posed by the author in 1873, but not yet published : it con- 

 sists essentially in throwing a beam of light vertically, or 

 at any determined angle, by means of the reflectors used in 

 public illuminations ; an observation from a neighboring sta- 

 tion of the spot of light on the under surface of the clouds 

 gives their altitude; so that both by day and night the ele- 

 vations may be determined. The formula?, etc., for use in 

 applying the photographic camera to this purpose during 

 the daytime were communicated by the author in 1871. 



Captain Miejahr gives in the Hansa a series of articles on 

 clouds and winds of the coasts of China and Japan, which 

 will be found to be eminently instructive. 



The importance of systematic observations on the move- 



