2 



Prof. W. N. Hartley. 



[Dec. 11, 



from wave-length 4414*5 to 2145*8. The prominent lines of cadmium 

 are distinguished by their extension across the spectrum from pole to 

 pole, while those of lead are on one side only and those of tin on the 

 other. As a weaker continuous spectrum fills the intervals between 

 the lines, there is no difficulty in obtaining accurate measurements. 

 To secure well-defined spectra the photographs were taken with the 

 solutions placed in front of the slit, upon which the rays from the 

 sparks were concentrated by a quartz lens of 2 inches diameter 

 and 3 inches focal length. The spectra were measured by means of 

 an ivory scale applied to the surface of the photographs ; this had 

 bevilled edges and was divided thereon into hundredths of an inch. 

 The linear measurements are termed scale numbers and are arbitrary, 

 but they were reduced to wave-lengths by the use of an interpolation 

 curve. The oscillation frequencies were also read off on a second 

 curve whenever it was considered desirable to record them. The 

 wave-lengths were taken from those published in the " Philosophical 

 Transactions," vol. 175, p. 63, 1884, but for use in recording these 

 measurements the fractions of a tenth-meter were disregarded. The 

 total number of lines employed, including two or three air-lines, was 

 seventy. For the convenience of those who maybe engaged in similar 

 work, the wave-lengths of the lines and their reciprocals are given 

 on page 3. The wave-lengths of a magnesium line and a calcium 

 triplet are also inserted, as it is sometimes convenient to refer to them. 



The absorption curves which have been drawn differ from those 

 figured in my previous communications, owing to the use of wave- 

 length numbers. The curves have been made continuous, and so the 

 necessity for shading has been avoided ; but very careful descriptions 

 of the spectra are furnished in addition, so that no detail has been 

 omitted. Nearly all the samples of alkaloids examined were obtained 

 from Messrs. T. and H. Smith and Co., of Edinburgh, Mr. David 

 Howard, of the firm of Howard and Sons, of Stratford, and Dr. C. R. A. 

 Wright, F.R.S. The bodies may be divided into two groups, those 

 which exhibit spectra with absorption-bands and those with con- 

 tinuous spectra. 



Alkaloids and Derivatives exhibiting Absorption-bands. 



Aconitine. Oxynarcotine. 



Pseudaconitine. Apomorphine Hydrochloride. 



Japaconitine. Cotarnine Hydrobromide. 



Morphine. Tetracetyl Morphine. 



Narcotine. Diacetyl Codeine. 



Codeine. Quinine. 



Thebaine. Quinine Sulphate. 



Papaverine. Cinchonine Sulphate. 



