HOUSE-MARTINS, III 
by choice in or over a porch or doorway, whether of 
house or stable, or over a window—somewhere where 
man is about. It is curious that in this country, so sub- 
ject to cold and cold winds, so many houses are built to 
face north or east, and this fact often compels the house- 
martin to build that side, the back of a house being fre- 
quently obstructed. In the case of house No. 1 there 
was a clear take-off on the north side, also with the 
stable. Houses are generally built to face the road, 
quite irrespective of the aspect, which custom is the 
origin of many cheerless dwellings. I think that house- 
martin fledglings and eggs are capable of enduring the 
utmost heat of our English summer, and the nests found 
deserted were abandoned for some other reason. More 
likely that the deficiency of insect food caused by the in-: 
clement weather weakened the parent. Sometimes these 
harmless and useful birds are cruelly shot. I have never 
seen a nest injured by heats; on the contrary, I should 
imagine that heat would cause the mortar to cohere 
more firmly, and that damp would be much more likely 
to make it unsafe. At house No. 2 the heat in the angle 
of the two walls was scarcely bearable on a July day 
If a nest were taken down and put in an oven I should 
doubt if it would crack. In nature, however, everything 
depends on locality. The roads in that locality were 
mended with flint, and the mortar from puddles appeared 
to make good cement. Possibly in some districts there 
may be no lime or silicon, and the mortar the birds use 
may be less adherent. The more one studies nature the 
more one becomes convinced that it is an error to sup- 
pose things proceed by a regular rule always applicable 
everywhere. All creatures change their habits with cir- 
cumstances ; consequently no observation can be accepted 
as final. 
