52 
NATURAL HISTOllY OF SELBOENE. 
and it will be worth your pains to endeavour to trace from whence they 
come, and to inquire why they make so very short a stay. 
In your account of your error with regard to the two species of 
herons, you incidentally gave me great entertainment in your 
description of the heronry at Cressi Hall ; which is a curiosity I never 
could manage to see. Fourscore nests of such a bird on one tree is a 
rarity which I would ride half as many miles to have a sight of. 
Pray be sure to tell me in your next whose seat Cressi Hall is, 
and near what to^n it lies.^' I have often thought that those vast 
extents of fens have never been sufficiently explored. If half a dozen 
gentlemen, furnished with a good strength of water-spaniels, were to 
beat them over for a week, they would certainly find more species. 
There is no bird, I believe, whose manners I have studied more than 
that of the capriwulgus (the goat-sucker), as it is a wonderful and 
curious creature ; but I have always found that though sometimes it may 
chatter as it flies, as I know it does, yet in general it utters its jarring 
note sitting on a bough ; and I have for many an half hour watched it 
as it sat with its under mandible quivering, and particularly this 
summer. It perches usually on a bare twig, with its head lower than 
its tail, in an attitude well expressed by your draughtsman in the folio 
" British Zoology." This bird is most punctual in beginning its song 
exactly at the close of day ; so exactly that I have known it strike up 
more than once or twice just at the report of the Portsmouth evening 
gun, which we can hear when the weather is still. It appears to me 
past all doubt that its notes are formed by organic impulse, by the 
powers of the parts of its windpipe, formed for sound, just as cats pur. 
You will credit me, I hope, when I assure you that, as my neighbours 
were assembled in an hermitage on the side of a steep hill where we 
drink tea, one of these churn-owls came and settled on the cross of 
that little straw edifice and began to chatter, and continued his note for 
many minutes ; and we were all struck with wonder to find that the 
organs of that little animal, when put in motion, gave a sensible 
vibration to the whole building ! This bird also sometimes makes a 
small squeak, repeated four or five times ; and I have observed that to 
happen when the cock has been pursuing the hen in a toying way 
through the boughs of a tree. 
It would not be at all strange if your bat, which you have procured, 
should prove a new one, since five species have been found in a 
neighbouring kingdom. The great sort that I mentioned is certainly a 
non-descript ; I saw but one this summer, and that I had no opportunity 
of taking. t 
Your account of the Indian grass was entertaining. I am no 
angler myself ; but inquiring of those that are, what they supposed 
that part of their tackle to be made of ? — they replied, " Of the intestines 
of a silkworm." 
Though I must not pretend to great skill in entomology, yet I cannot 
say that I am ignorant of that kind of knowledge ; I may now and then 
perhaps be able to furnish you with a little information. 
* Cressi Hall is near Spalding, in Lincolnshire, 
t Se^ Letters XX VL, XXXVL, and note. 
