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POPULAR SCIENCE REVIEW. 
stone we found it warm (milk warm) but not enough to be inconvenient. 
The next day it was given up to Lord Hawarden.” 
How to equalise the temperature of Rooms. — The late Mr. Appold, whose 
house was always one of the London curiosities from the circumstance that 
it was ventilated throughout by means of steam apparatus, invented a most 
ingenious automatic instrument for equalising and maintaining a fixed tem- 
perature of a room. The apparatus has been presented by his widow to the 
Royal Society, and was fully described at a recent meeting by Mr. Gassiot. 
The instrument consists of a glass tube having bulbs at each end. The tube 
is filled, as also about half of each bulb, with mercury, the lower bulb con- 
taining ether to the depth of half an inch, which floats on the mercury. The 
tube is secured to a plate of boxwood, and supported on knife-edges, on 
which it turns freely. At the end of the plate underneath the highest bulb, 
is a lever, to which a string is attached. This string is earned, by means 
of bell-cranks, to the supply- valve of a gas-stove or the damper of a furnace. 
The instrument acts' in the following manner : Supposing the stove to be 
lighted and to have raised the temperature more than is required, the heat 
will convert a portion of the ether in the lower bulb into vapour. The 
expansion of this vapour drives a quantity of the mercury out of the bulb 
underneath it through the tube into the upper bulb. Thi end to which 
the mercury has been driven being thus rendered the heaviest falls, and 
motion being communicated by the lever to the string, this closes the 
supply-valve or damper of the stove or furnace. Of course, if this should 
be carried beyond the required extent, the reverse action will take place. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Artificial Birds' Nests. — The societies formed for the protection of insecti- 
vorous birds in Switzerland, are now setting up artificial nests. One of the 
members of a society of this description, who lives in Vevey, having observed 
that many species of the kind mentioned select for nests the holes they find 
in the branches of rotten trees, and that they consequently do not find it 
easy to settle in orchards, where all the trees are in good condition, began, 
twenty-five years ago, to set up rotten trunks in his grounds $ and since then 
he has had no need to trouble himself in the least about clearing away 
caterpillars, that care being entirely left to the birds, who perform their 
duty admirably. His neighbours, on the contrary, who have not had this 
foresight, have had their orchards laid waste by insects. The Yverdun So- 
ciety have gone the length of placing artificial nests even in the public 
walks and communal forests, on the borders of the lawns, &c. All those 
nests are now inhabited by hedge-sparrows, redstarts, creepers, aud tomtits, 
all which may be found in Switzerland as high up as the perpetual snow- 
line. The same practice has found its way into Germany. 
The Darwinian Theory and the Heliconidce. — Mr Wallace brought before 
the British Association the following facts confirmatory of the Darwinian 
theory relating to the Heliconidae, one of the family of Lepidiptera. The 
Heliconidae, a group of butterflies with a powerful odour, such as to cause 
