XXIV. INTRODUCTION. 



finest of the whole year, and though the nights 

 may yet be chilly the days are temperate, and the 

 whole country smelling sweetly of newly opened 

 blossoms, and ornamented with young leaves, and 

 filled with the music of birds, is truly the season 

 of poetical love. 



i\TMOSPllERE. — There is not so much differ- 

 ence between the temperature of the lower and 

 higher parts of the air at this time of year, as in 

 autumn, as was ascertained by Dr. Forster who, 

 on the 30th of April, 1831, ascended in an air 

 balloon to a very great height. 



Natural History. — The most remakable 

 thing in this season is the return of the vernal 

 songsters who, arriving m succession, fill our 

 gardens, fields, and groves with their minstrelsy. 

 The least willow wren sylvia hippolais comes 

 first, the nightmgale, the redstart, the cuckoo, the 

 wryneck, and others in succession. The chimney 

 swalloAv hirundo rustica comes about April 15, 

 the house martlet h. urbica a little later, then comes 

 the sand martin h. climcola, and lastly the swift 

 h, apus. The first appearance of these birds, 

 particularly the swallow, is always hailed witl? 

 great pleasure by the naturalist, and followed as it 

 is by the song of the cuckoo from the blossomed 

 orchard, and by all the beauties of the vernal sea- 

 son, it is no wonder that in all ages it should have 

 been anticipated with delightful expectation. The 



