82 On Coloured Shadows. 



the point of saturation under the original volume. The want 

 of attention to this distinction frequently leads to important 

 errors. 



My object in the preceding pages, has been rather to state 

 what appeared to be matter of fact, than to throw out a mass of 

 random hypotheses. But this paper, having been drawn up be- 

 fore the article on the air-thermometer in the last Number of this 

 Journal, is more conformable to the common theory of that in- 

 strument. It is only the formulae near the end that could be 

 affected by this circumstance ; and within the limited range of 

 atmospheric temperatures, the difference on these formulae would 

 .not be material. At any rate, till the weight of moisture which 

 can exist in the air at different temperatures be better deter- 

 nfined, it is impossible to construct either rules or formulae which 

 can be depended on with perfect confidence. 



On Coloured Shadows. By Messrs Zschokke and Treschsel 



Junior *. 



X HERE appeared at Aran, at the commencement of the pre- 

 sent year, a memoir upon coloured shadows, read by Mr 

 Zschokke to the Society of Natural Sciences of that city. It 

 was received with the interest which attaches to all the produc- 

 tions of its author, productions so numerous and so varied that 

 one can scarcely believe them to proceed from the same pen. 

 Nor was this the first time that Mr Zschokke, the historian, 

 politician, economist, novelist, &c. bestowed some moments upon 

 the Sciences properly so called ; several scientific memoirs form 

 partof the collection of his works, and bear testimony in favour 

 of the general nature of his acquirements. 



The opinion entertained by Mr Zschokke on the subject of co- 

 loured shadows, was destined to meet with opposition. Mr 

 Treschsel, son of the learned professor of Berne, to whom we owe 

 the triangulation of a portion of our territory, and several other 



• Extract of a Memoir of M. Zschokke, entitled, »' Die farbigen Schatten, &c. 

 Arau 1826 ,•" and of a refutation of that memoir, by Mr F. Treschsel ^mw. 

 4 



