414 On the Experimental Relations [1857. 



has become clear, it is seen that the ruby portion below is as a 

 cloud sinking from it ; and in the part which has apparently 

 been cleared from colour by the settling of the particles, 

 the lens and cone of light still show the few, or rather the 

 fine diffused particles yet in suspension, though the proto~ 

 chloride of tin can show no gold in solution. The mould or 

 mucus before spoken of, often collects the larger, heavier 

 particles, and becomes of a dark blue colour ; it may then be 

 taken out by a splinter of wood, and being shaken in water, 

 disengages the particles, which issue from it in clouds like the 

 sporules from a ripe puff-ball. 



A gradual change goes on amongst the particles diffused 

 through these fluids, especially in the cases where the gold is 

 comparatively abundant. It appears to consist of an aggrega- 

 tion. Fluids, at first clear or almost clear to ordinary obser- 

 vation, become turbid ; being left to stand for a few days, a 

 deposit falls. If the supernatant fluid be separated and left 

 to stand, another deposit may be obtained. This process may 

 be repeated, and whilst the deposition goes on, the particles 

 in the fluid still seem to aggregate ; it is only when the fluid 

 is deprived of much gold that the process appears to stop. 

 Even after the fluid has attained a fine marked ruby tint, if 

 allowed to stand for months in a place of equable temperature, 

 the colouring particles will appear in floating clouds, and 

 probably the aggregation is then still going on. That the 

 particles of gold when they touch each other do in many cases 

 adhere together with facility, is shown in many experiments. 

 In order to test this matter mechanically, I gave much agitation 

 to a dense ruby fluid, but did not find it cause any sensible 

 change in the character. When gold particles of a much 

 larger size were agitated in water, they did cohere together, 

 and the fluid, which required a certain time for settling at the 

 beginning of the experiment, settled in a much shorter time at 

 the termination. 



If these fluids be examined generally their appearances differ 

 not merely under different circumstances, but also under the 

 same circumstances, though they always consist of a colourless 

 liquid and diffused particles of gold. A certain fluid in a bottle 

 or glass, looked at from the front, i. e. the illuminated side by 

 general daylight, may appear hazy and amethystine, whilst in 



