180 THE NATUEAL HISTORY 



wards, that some latitude must be admitted of in the distance of 

 echoes according to time and place. 



When experiments of this sort are making, it should always 

 be remembered that weather and the time of day have a vast 

 influence on an echo ; for a dull, heavy, moist air deadens and 

 clogs the sound ; and hot sunshine renders the air thin and weak, 

 and deprives it of all it's springiness ; and a ruffling wind quite 

 defeats the whole. In a still, clear, dewy evening the air is 

 most elastic ; and perhaps the later the hour the more so. 1 



Echo has always been so amusing to the imagination, that the 

 poets have personified her ; and in their hands she has been the 

 occasion of many a beautiful fiction. Nor need the gravest man 

 be ashamed to appear taken with such a phenomenon, since 

 it may become the subject of philosophical or mathematical 

 inquiries. 



One should have imagined that echoes, if not entertaining, 

 must at least have been harmless and inoffensive ; yet Virgil 

 advances a strange notion, that they are injurious to bees. After 

 enumerating some probable and reasonable annoyances, such as 

 prudent owners would wish far removed from their bee-gardens, 

 he adds 



" aut ubi concava pulsu 



"Saxa sonant, vocisque offensa resultat imago." 2 



This wild and fanciful assertion will hardly be admitted by 

 the philosophers of these days ; especially as they all now seem 

 agreed that insects are not furnished with any organs of hearing 

 at all. 3 But if it should be urged, that though they cannot hear 

 yet perhaps they may feel the repercussions of sounds, I grant it 

 is possible they may. Yet that these impressions are distasteful 

 or hurtful, I deny, because bees, in good summers, thrive well in 

 my outlet, where the echoes are very strong : for this village is 



1 [Tyndall's experiments have shown that there is no connection between a clear 

 atmosphere and ready transmission of sound. Rain, hail, snow and fog have no 

 power to obstruct sound, but " acoustic clouds," due to differences of heat or water- 

 vapour, may render days of extraordinary optical transparency days of equally 

 extraordinary acoustic opacity. (Lectures on Sound ; Lecture VII.).] 



^[Georgics, iv., 19.] 



3 [It is now known that certain insects possess elaborate organs of hearing. 

 The experimental proof that they are really concerned with the perception of sound 

 is particularly clear in the case of the male gnat, where the organ is lodged in an 

 enlarged joint at the base of the antenna. Auditory organs have also been described 

 in the forelegs of crickets and grasshoppers, as well as in the first abdominal seg- 

 ment of locusts.] 



