4 



Lieut. -General Sabine on the Results of [June 17, 



late Foreign Member, Mr. A. T. Kupffer, and ably superintended by him for 

 several years until his decease. I had been assured by M. Kupffer that I 

 might thoroughly rely on the observations made at these two stations ; and 

 I have since acquired experimentally the fullest confirmation of this assu- 

 rance in the case of Nertchinsk (as regards the magnetical, and inferen- 

 tially therefore also as regards the meteorological observations), by the 

 very delicate and sufficient test adverted to in page 238 of Art. VI. in the 

 Phil. Trans, for 18G4. Barnaoul is in lat. 53° 20', corresponding with the 

 rough average of the latitudes of our British stations generally, and is 400 

 feet above the sea. Nertchinsk differs only 10' from the latitude of Kew, 

 but has otherwise a marked feature of diversity in being at an elevation of 

 2230 feet, whilst Kew is only 34 feet above the sea-level. At Kew we 

 have only as yet available the records of a single year, necessarily in- 

 fluenced by the natural irregularities which cause one year to differ from 

 another. These irregularities are lessened, in the case of the Siberian sta- 

 tions, by combining in the present paper the results of two years of obser- 

 vation. 



I may now proceed to the Table of the Diurnal Variations, and to 

 a brief notice of the most salient features presented by the comparative 

 view of the phenomena of the three stations as shown in that Table. 



In discussing the diurnal variations of the meteorological elements, it is 

 customary to commence with the te?nperature, regarding it as in a great 

 degree the governing agent in regulating the phenomena of those other ele- 

 ments which are the subjects of the photographical registration. In the 

 middle latitudes, with which alone we have at present to deal, the diurnal 

 variation of the temperature is recognized as a single progression, having 

 one ascending and one descending branch, the turning-points being a 

 maximum at an early hour in the afternoon, and a minimum at a little 

 before sunrise. "We find this to be the order of the phenomena at the three 

 stations under review, viz. a maximum between 2 and 3 hours, and a 

 minimum between 16 and 1/ hours (4 and 5 a.m.), the range between 

 the extremes presenting, however, very marked differences, being 1 0°* 7(Fahr.) 

 at Kew, 14 o, 0 at Barnaoul, and l/°0 at Nertchinsk. 



It has been the practice for the last thirty years, at the principal European 

 observatories, to regard the elastic force of the aqueous vapour as an im- 

 portant meteorological element, and to employ it in the separation of the 

 barometric pressure into its two constituents, viz. the pressure of the dry 

 air, and the elasticity of the aqueous vapour mingled therein*. In con- 

 formity with this practice, we may take the vapour tension next in the order 

 of succession. It was remarked by Bessel, in the Astron. Nach. for 1838 

 (No. 35G), that "since the invention of Daniell's hygrometer and August's 

 psychrometer, we possess the means of ascertaining at all times with ease 

 and sufficient exactness the quantity of aqueous vapour contained in the 



* In the publications of the British Colonial Observatories (1840 -1847) this method 

 was adopted in the meteorological reductions, being one of its earliest applications. 



