OF ATMOSPHERIC PRESSURE IN EUROPE, ETC. 261 



The curves laid down from the numbers in this table are 

 exhibited in the plates which accompany this paper, and a 

 slight inspection will show that in all of them a principal 

 minimum occurs in one of the three summer months, 

 June, July, or August, but generally in July, the warmest 

 month of the year ; and in many of them there is a second 

 minimum occurring in one of the two winter months, 

 January or February. With respect to the two maxima 

 which occur between these minima, it will readily be ob- 

 served that the interval between their summits gradually 

 increases as we advance from the eastern to the western 

 stations. Thus, at Nertchinsk, the first maximum occurs 

 in the middle of April, and the second about the second 

 week in November, the interval being nearly seven months j 

 at Irkoutzk the first maximum occurs at the end of March 

 or beginning of April, and the second maximum in the 

 middle of November, the interval being seven and a half 

 months; at Barnaoul the first maximum takes place in 

 the middle of March, and the second in the middle of 

 November, the interval being eight months ; at Catherin- 

 bourg the first maximum occurs in the second week of 

 March, and the second about the second week of Decem- 

 ber, the interval being nine months ; at Tiflis, a station 

 between the Black Sea and the Caspian, and at Lougan in 

 southern European Russia, the interval is also about nine 

 months; at St. Petersburgh the first maximum occurs in 

 the third week of February, and the second in the second 

 week of December, the interval being thus about nine and 

 a Aa/f months; at Stockholm the first maximum occurs in 

 the middle of February, and the second in the middle of 

 December, the interval is therefore ten months ; at Milan 

 the interval is also about ten months ; but at the western 

 stations, Sandwick in Orkney, Greenwich and Dublin, we 

 have only one principal maximum, which occurs about the 

 second week of January, and which appears to be formed 



