518 Notices respecting New Books. 



midity in the quarter ending March 31, 1848, was 0'888. 

 The mean amount of vapour mixed with the air would have 

 produced water, if all had been precipitated at one time on 

 the surface of the earth, to the depth of (in the quarter ending 

 March 31, 1848) 3 '25 inches. And these values for Cornwall 

 and Devonshire were 2-7 grains ; 0-5 grain ; 0-863 grain ; and 

 3"6 inches. 



The results from the station in Ireland, depending on the 

 temperature of the air, the direction of the wind, and the 

 amount of clouds, agree with those in England at the same 

 latitude ; but the res'ults which depend on the humidity of the 

 air and the amount of rain, exhibit an excess over those in 

 England, and the daily and monthly ranges of the readings 

 of the thermometer are less than those in England. 



May 25, 1848. 



LXVIII. Notices respecting New Books. 



Results of Astronomical Observations made during the years 1834, 

 1835, 1836, 1837, 1838, at tlie Cape of Good Hope; being the 

 Completion of a Telescopic Survey of the whole Surface of the visible 

 Heavens, commenced in 1825. By Sir John F. W. Herschel, 

 Bart., K.H., S^c. &;c. London: Smith, Elder and Co. 1847. {Se- 

 cond notice.^ 



Chap. II. Of the Double Stars of the Southern Hemisphere. 



IN the Introduction to the Catalogue of Southern Double Stars 

 the author observes, that as the principal object kept in view by 

 him during the progress of his southern sweeps was the discovery of 

 new nebulfe, or the determination of the places of those already 

 known, the detection and measurement of double stars was regarded 

 as of subordinate interest, and allowed to interfere as little as possible 

 with what was looked upon as the main inquiry. When nebulae were 

 expected, and especially on new ground, little leisure was afforded 

 for any minute examination of stars ; but in regions which had been 

 already examined, or where nebulse were thinly scattered, stars down 

 to the sixth or seventh magnitude were seldom dismissed till they 

 had undergone the appUcation of one or more of the diaphragms. 

 To have executed a regular review of the southern heavens with the 

 20-foot reflector, for the purpose of detecting close double stars, 

 would have required at least two additional years, probably more. 

 When double stars occurred they were of course always taken, and 

 a measured angle of position secured as accurate as a single rapid 

 setting of the wires afforded ; but excepting in special circumstances 

 no close examination was made, unless some suspicion, excited under 

 the ordinary sweeping power (180), induced an application of high 

 ma^-nifying powers, and in such cases it would occasionally happen 

 that a long and pertinacious scrutiny took place. 



