Of five houses, a stable, and chapel wall, much frequented by martins, the aspects were as follows:--House No. 1, nests on the north side, south side, and east, both the south and east very warm; No. 2, on the south and east walls--these walls met in an angle, and as it were enclosed the sunbeams, making it very heated sometimes; No. 3, on the south and west walls, the warmest sides of the building; No. 4, all along under the southern eaves, a very warm wall; No. 5, also under the southern eaves, and not elsewhere. The stable fronted south; there were nests front and back, north and south; the chapel eave that was frequented faced towards the west. In the case of several other houses the nests were on the sunny side; but I am not so well acquainted with the localities. So far as my observation goes, I think the house-martin--with all the swallow tribe--prefers warmth, and, if possible, chooses the sunny side of a building. A consideration, however, that weighs much with this bird is the character of the take-off; he likes a space immediately in front of his nest, free of trees or other obstructions, so that when rushing out from his little doorway he may not strike against anything. For ages it has also been remarked that the house-martin likes the proximity of man, and will build 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 subject 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 frequently 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 inclement 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 suppose things proceed by a regular rule always