562 Proceedings of the Royal Society 
had no further acquaintance with the hill structure around than 
that of an angler thirty years ago, when I probably looked more 
at what came out of the loch than at anything else concerning 
it. I consequently went prepossessed in its favour by the glowing 
account given of its extreme purity by its admirers. My surprise, 
therefore, was not small when my very first observation showed 
that its water was yellow. My visit was made in circumstances 
highly favourable to its condition, in splendid sunshine, being the 
last two days of six weeks of extraordinarily dry weather, broken 
only by a few light showers, sufficient to freshen the grass, and 
little more. But I found that my white porcelain basin became at 
once yellowish when dropped into the lake, acquired a lively amber 
hue at the depth of 3 feet, and disappeared entirely at 12 feet, 
while the sun shone brightly on the spot. I remembered well, 
however, having once distinguished small pebbles in the Dumfries- 
shire Esk through 16 feet of water, when spearing salmon in a still 
pool, and on another occasion through 21 feet in a pool below the 
Bracklinn Falls, near Callander. I afterwards tested the colour of 
the loch water on a small scale, and showed it satisfactorily to 
many, by comparing it with the water of Edinburgh of the same 
date in two narrow glass jars, 20 inches in height, with a circular 
disc of white porcelain at the bottom. The porcelain was of un- 
stained whiteness as seen through the Edinburgh water, but of a 
lively amber tint when looked at through the water of St Mary’s 
Loch. The difference was not less marked in the narrow 16-inch 
tubes. Even in dining-table water-bottles, placed on a white table- 
cloth, the colour of the loch water was such as to make it evident, 
that certainly nobody would drink it who could get the other. I 
may add that, when I revisited the loch on 8th September, also 
in bright sunshine, I found that my porcelain basin disappeared 
entirely in eight feet of water ; and, nevertheless, there had been 
previously ten continuous days of absolutely dry weather. 
On the 12th and 13th June, I saw in the water no want of the 
water-fleas, which excited so much interest and heat in the late 
controversy. It may create additional interest with some to be 
told that three months later they were decidedly bigger, busier, 
and altogether more deserving of their vernacular name. 
Before speaking of the chemical composition of the water, let 
