410 Jtev, Mr, Emmett^s Observations [Dec. 



In the course of experiments which led me to the adoption of 

 the plan recommended in this essay, I have accumulated a 

 number of comparative analyses of the several astringents used 

 in the arts, made with a view to ascertain how the test would 

 work in all cases, as an index to their tanning properties. 



These I intended to annex to the present paper, but satisfied 

 of the correct action of the test, I omit them for the present, 

 convinced that each individual lot of astringent substance 

 brought to market may dili'er so widely in composition and 

 quality from every other, that such a table as I might be able to 

 form from the examination of particular samples (not now at 

 market) would only tend to mislead- 



My chief hope is, that in the preceding sketch of a process, I 

 have been sufficiently explicit to enable a tanner to proceed for 

 himself towards the attainment of that important object, — a 

 knowledge of the comparative value of all the astringent mate- 

 rials which appear at market, in time to regulate his purchase of 

 any. Edward Bell Stephens. 



Article II, 



Ohsenmtions on the Planet Venus ^ made during the Spring of the 

 Year 1 825. By the Rev. J. B. Emmett. 



(To the Editors of the Annals of Philosophy/.) 



GENTLEMEN, Great Omeburn, Sept. 9, 1825. 



Since the time of Cassini, spots on Venus have rarely been 

 seen. Dr. Herschel says, the planet has always presented to 

 him a perfectly uniform surface, quite free from spots ; and the 

 only observations made since those of Cassini and Bianchini 

 were by Short, who was fortunate enough once to see them. 



During the spring of the present year, Venus was rarely 

 entirely free from them, and, therefore, I hope, that my obser- 

 vations may not be the whole that have been made. The 

 instruments I employed were an excellent Newtonian reflector 

 of 6 inches aperture, using powers from 70 to 400 ; an aerial, 

 not achromatic, of 18 feet focus, with powers of 70 to 150 ; an 

 aerial of 50 feet, power 160 ; and I hope I shall be able to show 

 that where the old aerial telescope has sufficient light and power, 

 it possesses some very considerable advantages over other 

 instruments. 



Before I proceed with the immediate subject of this paper, it 

 will be proper to convey a correct idea of the goodness of the 

 instruments, to remove all doubts which otherwise rnight arise. 

 With the reflector, with powers from 70 to 800, and occasionally 

 1200, 1 have repeatedly seen the double stars Castor, « Herculis^ 



