430 FRAGMENTS OF SCTENCK. 
is established and the chill disappears. Some years ago 
I witnessed Mr. Hirst experimenting at Zermatt on the 
turbid water of the Visp. When kept still for a day or so, 
the grosser matter sank, but the finer particles remained 
suspended, and gave a distinctly blue tinge to the water. 
The blueness of certain Alpine lakes has been shown to be 
in part due to this cause. Professor Roscoe has noticed 
several striking cases of a similar kind. In a very remark- 
able paper the late Principal Forbes showed that steam 
issuing from the safety-valve of a locomotive, when favor- 
ably observed, exhibits at a gertain stage of its condensation 
the colors of the sky. It is blue by reflected light, and 
orange or red by transmitted light. The same effect, as 
pointed out by Goethe, is to some extent exhibited by peat- 
smoke. More than ten years ago, I amused myself by 
observing, on a calm day at Killarney, the straight smoke- 
columns rising from the cabin-chimneys. It was easy to 
project the lower portion of a column against a dark pine, 
and its upper portion against a bright cloud. The smoke 
in the former case was blue, being seen mainly by reflected 
light; in the latter case it was reddish, being seen mainly 
by transmitted light. Such smoke was not in exactly the 
condition to give us the glow of the Alps, but it was a step 
in this direction. Briicke's fine precipitate above referred 
to looks yellowish by transmitted light; but, by duly 
strengthening the precipitate, you may render the white 
light of noon as ruby-colored as the sun, when seen through 
Liverpool smoke, or upon Alpine horizons. I do not, how- 
ever, point to the gross smoke arising from coal as an illus- 
tration of the action of small particles, because such smoke 
soon absorbs and destroys the waves of blue, instead of 
sending them to the eyes of the observer. 
These multifarious facts, and numberless others which 
cannot now be referred to, are explained by reference to 
the single principle, that, where the scattering particles 
are small in comparison to the ethereal waves, we have in 
the reflected light a greater proportion of the smaller waves, 
and in the transmitted light a greater proportion of the 
larger waves, than existed in the original white light. The 
consequence, as regards sensation, is that in the one case 
blue is predominant, and in the other orange or red. Our 
best microscopes can readily reveal objects not more than 
one-fifty-thousandth of an inch in diameter. This is less. 
