38 DR. JAMES BOTTOMLEY^S 



to each other. Hence it is impossible to form any idea 

 from the temperature of a winter what kind of summer 

 temperature may follow. 



I have shown on the same diagram the mean tempera- 

 ture of each year from 1861-1878. The mean of all is 48°. 

 The ratios of their differences are extremely small^ so small, 

 indeed, as to be of no practical value ; for between the 

 coldest year and the warmest of the last seventeen years 

 there is a difference of only 2°'(), and the mean difference 

 of temperature of all these years amounts to only o°'3. 

 These differences do not, from the data I have, seem to 

 observe any definite rule. 



VI. Colorimetrical Experiments. — Part II. 

 By James Bottomley, B,A., D.Sc, T^.C.S. 



Eead before the Physical and Mathematical Section, 

 April 22nd, 1879. 



In a short note which I read before this Society (vol. xv. 

 p. 63) I proposed to measure quantities of colouring- 

 matter in solution, using the formula qt = q't'm. the calcu- 

 lation, q and q' denoting quantities of colouring-matter, 

 t and t' lengths of columns of coloured fluid, the colour- 

 ing-matters being dissolved in equal volumes of water. 

 Last session I gave the results of some experiments which 

 I had obtained two years previously. Lately I have made 

 some further experiments, which I give in this paper, along 



