5036 THE ZooLocist—Auveust, 1876. 
“Tf it be urged that small reservoirs may be made to do as makeshifts, 
because money and space for them cannot be afforded, there is some kind 
of reason in that. But if it be averred to the contrary as a principle, then 
that indicates a singular amount of no knowledge which, if possible, is 
something more than wonderful. My arguments are founded on the clear 
and simple obviousness of the fact that a given quantity of dead organic 
matter diffused through a large quantity of water sullies it less than if it 
were small, and on the necessity of maintaining an evenly moderate tempera- 
ture for the reasons already given, avoiding the high and low ranges of the 
atmosphere; and I show that the easiest manner of attaining this is by 
having a large reservoir sunk in the earth at a distance giving a known 
temperature. ‘Thus, referring to the sunk thermometers at the Greenwich 
Observatory, with a thermometer having its bulb on a level with the scales 
of the sunk instraments, the lowest (January) mean monthly reading in a 
named year was 364° F’., with a mean daily range of 6°9° F.; and under 
the same circumstances the highest (July) mean monthly reading was 
669° F., with a mean daily range of 19°9°F. But from the showing of 
other thermometers whose bulbs are sunk in the ground to the respective 
depths of one inch, three feet, twelve feet, and twenty-five feet, the tem- 
peratures become strikingly even for the whole year through—so much so, 
that at twenty-five feet deep the mean monthly reading of January was 
52° F., with a mean daily range of only 0°025° F.; and the mean monthly 
reading of July was 49:0° I’., with a mean daily range of but 0-06° F., the 
highest mean daily range at that depth in any month of the year being 
007° F. in August.” 
“ Tndeed if a reservoir were one hundred times as large as the show 
tanks, and was kept at 50° F., then the tanks might be in an atmosphere 
at 212° F. (the heat of boiling water), and yet the water would be only 
52°12° F., and the most delicate English animals would live in it. 
In a note to a preceding passage Mr. Lloyd supplies the following 
further particulars as to the temperature of the water in the 
Crystal Palace Aquarium :— 
«The water in the Crystal Palace Aquarium has a very small range of 
from 52° F. in very cold, to 61° F. in very hot, weather. In April last 
(1876) we had, at Sydenham, blue skies, a bright sun, and an oppressive 
warmth, with 74° F. in the shade, on the 8th of the month. On the 12th, 
four days after, we had a leaden firmament, and clouds of blinding snow 
and sleet driven by a bitter north-east wind, with the thermometer at 29° F., 
giving so great a range as 45° I’. within a week. Yet the water in the 
aquarium had a range of only 1° F, = 54°F, to 53°F,” 
