Intelligence and Miscellaneous Articles. 329 



are the most powerful known to me. Glaciers and the sea shaped 

 Ireland, as I believe. Rivers and weathering have done little to 

 obliterate the tool-marks of ice and the sea since the end of the 

 last of a series of Glacial periods." 



XLI. Intelligence and Miscellaneous Articles. 



ON SOLUTION OF NITRATE OF NICKEL AS AN ABSORPTION- 

 PREPARATION. BY DR. H. EMSMANN. 



\ MONGr the colour-spectra exhibited by coloured liquids, that of 

 ■**■ the beautiful apple-green solution of nickel in nitric acid ap- 

 pears to me especially worthy of notice. Having filled a hollow 

 prism with this solution, I found that the terminal colours (red and 

 violet) in the spectrum were absorbed. This was new to me ; but 

 in Mousson's Physik auf Grundlage der Erfahrung this peculiarity 

 of the solution of nitrate of nickel is cited as a thing known. 



Now, while with most coloured liquids the colour results as a 

 mixture of all the spectral colours under the predominance of that 

 of the substance in question, we have here the beautiful green as a 

 mixture of the spectral colours with the exception of the red 

 and the violet. This fluid is therefore particularly well adapted and 

 convenient, not merely for showing in the course of instruction the 

 phenomena of absorption of colours, but also for ascertaining the 

 composition of the colours of substances. 



I keep, for the purpose of instruction, some of this solution 

 ready in a glass phial, the sides of which are as nearly as possible 

 parallel (I obtained such a one at a perfumer's), and use it for de- 

 monstrating the absorption. On pasteboard covered with black 

 paper narrow strips of coloured paper are pasted, among which are 

 different reds. One sort of red is not to be perceived through the 

 liquid ; a second appears dark blue ; a third, yellow. A violet 

 stripe is likewise not to be perceived ; a white stripe appears green. 

 Titles of books, printed in red, looked at through the liquid appear 

 dark ; and so do the red and violet parts on woollen embroidery. 



In most text-books of physics the phenomena of absorption have 

 till now been for the most part only briefly touched upon. Wiill- 

 ner's Lehrbuch der Experimentcdpliysilc forms an honouraWe excep- 

 tion, since in it are given not only the different methods of inves- 

 tigation, but also several examples of body-colours, with the account 

 of the colours from the mixture of which they result. Coloured 

 liquids generally seem to have been but little investigated. Mousson 

 cites didymium, chlorophyl, and blood. A comparison of the spectra 

 of coloured liquids would be very desirable. Solution of sulphate 

 of copper shows particularly violet, yellow, and blue in the spec- 

 trum, in about the proportion 7:5:2, and some red. In the spec- 

 trum of sulphate of iron, green predominates. Perrocyanide of 

 potassium gives red, green, violet, and dark blue. 



The purpose of this note is chiefly to call the attention of my 

 colleagues to the solution of nitrate of nickel, and to recommend 



