PHYSICS OF THE GLOBE. 167 



completely obscured by other influences, and that even in 

 the mean of nine cycles there is no certain evidence of any 

 definite relation ; to which conclusion Celoria had also come 

 in 1874, in reference to the temperatures of Milan. Hann 

 has also investigated the possibility of predicting the temper- 

 ature of any given season of the year from the known temper- 

 ature of the past season. He concludes that, on the whole, 

 when the temperature of any season is decidedly greater or 

 less than the normal temperature, it is more probable that 

 the following season will deviate in the same direction from 

 the normal. Similar results have been obtained by Quetelet 

 and Eisenlohr. In conclusion, he reduces the temperatures 

 hitherto observed in Vienna to the localitv of the new Mete- 

 orological Institute, on the Hohewarte, near Vienna. In a 

 subsequent paper on this same subject, Hann revises his 

 method of determining the mean temperature, inasmuch as 

 he considers that he may have been led into error by having 

 given too great weight to the long series of observations 

 made unfortunately with somewhat less perfect instruments 

 and under an objectionable exposure. 



The direct utilization of the solar heat for industrial pur- 

 poses a subject which has been diligently pursued for many 

 years by Mouchot forms the subject of a note by him read 

 before the Academy of Sciences, September 30, 1878, in which 

 he says that his smaller pieces of cooking apparatus have 

 never failed to work during sunny weather. Some mirrors 

 of less than half a square meter, constructed with all desira- 

 ble perfection, have sufficed to roast half a kilogram of beef 

 in twenty-two minutes, and to cook, in an hour and a half, 

 stews which required four hours of an ordinary fire of wood ; 

 and in half an hour to bring three fourths of a liter of cold 

 water to the boiling-point, which latter corresponds to the 

 utilization of 9.5 colories per minute per square meter a re- 

 markable result in the latitude of Paris. The solar alembics 

 have also furnished equally excellent results. Assisted by 

 Pifre, he had completely set up, on the 1st of September, a 

 solar receiver, whose mirror presents an aperture of about 

 twenty square meters. 



Of the innumerable inventions of the venerable John Erics- 

 son, he is, we believe, most fond of his inventions and research- 

 es relative to caloric and solar engines, and the direct utili- 



