1775 SWALLOW MONOGRAPHIES 295 



in Sweden ; and that Linnaeus never was witness himself to 

 such a murmur ; but takes his cue from some hasty and 

 inaccurate correspondent. 



I beg you would take two pieces of spunge of equal size, 

 weight and softness, and hang them by strings over an upland 

 pond in foggy weather ^ the one as near the surface as possible, 

 the other several feet ahove the water : then I desire you 

 would squeeze the spunges in a morning, and see which 

 produces the most water. Now if the lower spunge should 

 prove, from repeated trials, to be the moistest, I should hope 

 the fact would in some measure corroborate my suspicions, 

 that ponds, and pools do by condensation from the coolness of 

 their surfaces assimilate to themselves fogs and vapours by 

 contact and that is one reason why many very little upland 

 ponds, though subject to a continual waste by cattle, &c. ; 

 yet never fail in the severest droughts, while larger pools in 

 bottoms frequently become dry. But as your father and you 

 may most probably hit upon a better experiment, I desire 

 you would try such as you think most to the purpose. 

 Moreover, I desire that both of you would send me every 

 hint in Natural History that occurs to your minds after your 

 recent visit to these parts. My swallow monographies are 

 printed off by the R. S. in Vol. 65, p. 258 ; but the corrector 

 of the press has made sad work with my unfortunate letters ; 

 for in one place he makes me say that " swallows eat grass " 

 and in an other uses caves instead of eaves : moreover he has 

 transposed my letters so as to misplace them, though I 

 numbered them most exactly, and by that means has made a 

 jumble of dates ; besides putting two whens in one sentence ; 

 and many more inaccuracies too numerous to mention ! 

 fie ! for so young a man as you to use glasses that magnify 

 200 times, when Linn, planned and perfected his whole 

 sexual system nudis oculis. I wish you joy that Jupiter 

 is restored to his liberty and dignity, for the Cornish man 

 has seized on him, and appropriated him to himself as a 



