108 Migration of Swifts. 



the blind, and discovered one of the common large garden 

 snails crawling upon one of the panes. Immediately upon 

 my drawing up the blind, and the light of the candle being 

 strongly thrown upon the window, the sound ceased, and the 

 snail partly withdrew itself under its shell; nor were its 

 motions resumed so long as the light continued to be thrown 

 upon the window. Being now satisfied, however, that the 

 sound was caused by the motions of the snail on the pane of 

 glass, I carefully noticed the exact position of the animal ; 

 and, putting the candle in such a situation that no light 

 should be thrown upon the window, I returned to it, and sat 

 down close to the place where the snail was. In a few minutes 

 the sound returned, and I had now no farther doubt of its 

 being caused by the snail; for, bringing the candle back 

 again so as just to throw light enough upon the window to 

 enable me to perceive his motions, I observed that it was now 

 moving on again across the pane, and the sound evidently 

 accompanied it. Upon stopping its motion again as before, 

 the sound ceased ; but always returned when it moved on. I 

 suspected at the time, with the correspondent of the Natu- 

 ralist, that the sound proceeded from the snail itself, as I was 

 not able to ascertain whether the shell actually was in any 

 part in contact with the glass; but I concluded that this must 

 be the case, and that the sound was merely caused by the slow 

 scraping of the shell on the moistened surface of the glass, 

 producing a phenomenon somewhat similar to that which 

 children amuse themselves in producing by passing a wet 

 finger over the edge of a glass containing water. As far as I 

 recollect, it was always in wet weather when the pheno- 

 menon occurred j and when the whole surface of the glass 

 would be overspread with moisture. The above phenomenon 

 has been one of frequent occurrence since the time I first 

 noticed it; and, if it be traceable to the same cause as in the 

 other instance to which I have alluded, perhaps the body of 

 the animal might cause a sufficient vibration in the glass to 

 produce the sound, even if the shell were not in contact with 

 it. If you think the above observations calculated to throw 

 any light upon the subject, they are much at your service. — 

 T. Salwey. Vicarage Oswestry, Jan. 5. 1 837. 



Migration of Swifts. — I beg to offer, for insertion in your 

 Magazine, a few remarks relative to the autumnal migration, 

 &c, of the swifts (Cypselus murarius Temm.), in the years 

 1834, 1835, and 1836, in this vicinity. 



The excessively hot weather we experienced during the 

 summer of 1834, and, more particularly, about the time the 

 swifts usually leave this country, might naturally have been 



