Mrs. Somervilles Experiments. 279 



the solar spectrum, and that influences widely differing 

 from either light, heat or colour are transmitted to us 

 from our central luminary, which are mainly instrumental 

 in evolving and maturing the splendid hues of the 

 vegetable creation and elaborating the juices to which 

 they owe their beauty and their vitality. I think it 

 certain that heat goes for something in evaporating your 

 liquids and thereby causing some of your phenomena ; 

 but there is a difference of quality as well as of quantity 

 of heat brought into view which renders it susceptible of 

 analysis by the coloured juices so that in certain parts 

 of the spectrum it is retained and fixed, in others reflected 

 according as the nature of the tint favours the one or the 

 other. Pray go on with these delightful experiments. I 

 wish you could save yourself the fatigue of watching and 

 directing your sunbeam by a clock work. If I were at 

 your elbow I could rig you out a heliotrope quite 

 sufficient with the aid of any common wooden clock. 



Now I am going to take a liberty (but not till 



after duly consulting Mr. Greig with whose approbation 

 I act, and you are not to gainsay our proceedings) and 

 that is to communicate your results in the form of 

 " an extract of a letter" to myself to the Royal Society. 

 You may be very sure that I would not do this if I 

 thought that the experiments were not intrinsically quite 

 deserving to be recorded in the pages of the Phil. Trans. 

 and if I were not sure that they will lead to a vast field 

 of curious and beautiful research; and as ydu have 

 already once contributed to the Society, (on a subject 

 connected with the spectrum and the sunbeam) this will, 

 I trust, not appear in your eyes in a formidable or a 

 repulsive light, and it will be a great matter of congratu- 

 lation to us all to know that these subjects continue to 



