721 



sun rises later ; but the type * of summer 

 (+ 20 h ;-— 4g h ; + 10 h ) is almost identical in Eu- 

 rope with that which I ascertained in the torrid 

 zone (+ 20 b ;— 4i h ; -Hl h ). It would be interest- 

 ing* to know if this analogy holds at the epocha 

 of the minimum which takes place after mid- 

 night (16i h ), an epocha for which numerous 

 statements are wanting in our climates. 



A traveller who has devoted himself with 

 success to the measurement of mountains, M. de 

 Parrot ^ asserts, from a series of observations 

 which he made every half-hour, during 14 days 

 and 14 nights, that at Milan, the epochas of the 

 limits are : — I8 h ; + 23h ; 4* h ; + 12 h . It can- 

 not be doubted that, in studying the tables of 

 the horary variations of the barometer, publish- 

 ed nine years ago by M. Arago, and which I 

 regard* on account of the perfection of the in- 



* The type of the winter in Europe , taking the mean be- 

 tween the horary observations of MM. Ramond, Marque Vic- 

 tor, and Billiet, appears to be + 21| h ; — 2J h ; 4. 9| h . The dif- 

 ferences presented by the epocha of the limits in winter and in 

 summer seem to prove, that the most proper hours for ob- 

 servers of the barometer, in our observations in Europe, are 

 (if we would wish them to be uniform for the whole of the 

 year), 9| h in the morning 5 3^ afternoon 3 and 10£ h at night. 

 The minimum of the morning in Europe seems to fall be- 

 tween 3 h and 4 h after midnight. 



+ Reise in den Pyrenceen von Freidrich von Parrot, 1323, 

 p. 11. This maximum of the morning (one hour only be* 

 fore midnight) appears to me very late. 



VOL. VI. 3 B 



