50 THE ORIGIN OF LIFE 



to the ounce, after boiling for ten minutes, the 

 fluid with one sample had a pale port-wine colour, 

 with scanty deposit; with four drops to the ounce 

 the colour of the fluid was a gamboge yellow, and 

 the deposit more abundant; while with six drops 

 to the ounce the colour of the fluid, after the same 

 amount of heating, was pale yellow and opales- 

 cent, and the deposit still more plentiful. 



As the strength of different samples of the 

 sodium silicate varies so much, trials should be 

 made with solutions containing one, two, three, 

 and four drops to the ounce which have been 

 boiled for ten minutes, in order to ascertain the 

 number of drops of the dilute sodium silicate in 

 use that will give this kind of pale port-wine 

 colour to the solutions, together with only a very 

 scanty precipitate; as I have generally found such 

 solutions to be most productive. 



No variations of the kind to which I have been 

 referring are, of course, observable when dealing 

 with the colourless solution. Here it is only a ques- 

 tion of much or little deposit from the use of vary- 

 ing quantities of the dilute sodium silicate, together 

 with variations in the acidity or alkalinity of the 

 solutions, that can be observed. I may say, however, 



