224 Miscellaneous, 



lower part of the Upper Canada Drift to remove from the rela- 

 tions of these deposits in Upper and Lower Canada, all that am- 

 biguity which has so often been referred to in papers in this 

 Journal. In the mean time, we hail the labours of Prof. Chapman 

 and Mr. Bell as important contributions towards this end, and as 

 already pointing out a probable solution of the difficulty. 



J. W. D. 



MISCELLANEOUS. 



A few Notes on Analysis hy the aid of the Spectrum. 



As colour is so conspicuous a characteristic of many substances, 

 it is not surprising that the chemist largely avails him-elf of its 

 indications in qualitative analysis. These indications are, how- 

 ever, neither so reliable nor so extensively useful in chemical de- 

 terminations as might at first sight appear ; for in the first place, 

 the colours of many substances vary very much, according to their 

 state of aggregation, and to other circumstances not affecting 

 their chemical constitution, — in the second place, the colour of a 

 compound does not appear to be a resultant of the colours of its 

 elements, — and lastly, the unassisted eye is unable to distinguish 

 hues differing but slightly, unless opportunity for comj^arisou with 

 each other be afforded ; or, in case of compound tints, to deter- 

 mine the tints compoun led, as for instance, whether an olive 

 green result from an intermixture of violet and yellow, or of orange 

 and blue. 



Any inaccuracy arising from imperfection of the eye, can how- 

 ever be almost, if not altogether, eliminated by prismatic decora- 

 position of the light reflected from, or transmitted through the 

 coloured substance ; and by comparing the spectrum thus pro- 

 duced with the solar spectrum, the most precise information can 

 be obtained respecting the tint under examination. Thus, to recur 

 to the illustration adduced above, the different refrangibilities of 

 the component colours would enable us readily to distinguish the 

 one olive green from the other. Undoubtedly the best mode of 

 thus examining the colour of a substance, which is either a liquid 

 or capable of solution in a liquid, is that employed by Dr. Glad- 

 stone in his late researches on the absorption of light by coloured 

 media. In his experiments, a wide, thin beam of light was trans- 

 mitted through a long, narrow, and gradually tapering hollow 



