360 MISCELLANEA. 
been of a superior kind ; nor does old age in the dam in the least 
appear to militate against their thriftiness, contrary to the general 
opinion of breeders . — Cambridge Chronicle. 
Feeding Poultry. 
Professor Gregory, of Aberdeen, in a letter to a friend, 
observes, <c As I suppose you keep poultry, I may tell you that 
it has been ascertained, that if you mix with their food a suffi- 
cient quantity of egg-shells or chalk, which they eat greedily, 
they will lay, cceteris paribus , twice or thrice as many eggs as 
before. A well-fed fowl is disposed to lay a vast number of eggs, 
but cannot do so without the materials for the shells, however 
nourishing in other respects her food may be ; indeed, a fowl fed 
on food and water, free from carbonate of lime, and not finding 
any in the soil, or in the shape of mortar, which they often eat 
off the walls, would lay no eggs at all, with the best will in the 
world.” 
Vegetation protected by Snow. 
It is a common opinion, and with due limitation is no 
doubt correct, that a covering bf snow protects the earth and the 
vegetation upon its surface from the effects of intense frost. Not 
that the snow imparts warmth, but, being a bad conductor of ca- 
loric or heat, it checks the abstraction of that principle by the 
cold air above it. The following experiments may give some idea 
of it : they were made under favourable conditions, from the 
low temperature reached during the frost, and from the cir- 
cumstance that heavy snow fell immediately after a thaw, so 
that the surface of the ground was then at 32 degrees. 
About 11 a.m., the temperature of the air was 13 degrees 
(Fahrenheit) ; that of the surface of the snow was 12. The night 
had been much colder, and the surface had not then acquired, 
though I afterwards found that it quickly gained, the tempera- 
ture of the atmosphere; — 
The air then being at 13 
The surface of the snow 12 
At one inch in depth it was .... 15 
At two inches 20 
At three inches 24 
At four and five inches 26 
At six and seven inches 27 
At eight inches, near the bottom . . 28 
