40 
I have no douht that many of the “tarns,” or smaller Meres, so 
common on onr boulder clays, or “ heavy lands ” as they are com- 
monly termed, have been formed in a similar manner.* Water, in 
draining through chalk, will form the well-known “ sand-pipes,” 
by dissolving portions of the carbonate of lime away. I have seen 
sand-pipes so formed, wliich have been thirty yards across. The 
matter thus hollowed out and carried away is replaced by a subsi- 
dence of the overlying beds, Avhich then form tlie basin for a small 
IMere or tarn. We occasionally read in the newspapers of the 
“ caving in ” of earth in this fashion, and its cause is due to the 
igencies I have mentioned. 
In conclusion, I beg to thank you for your kindness in listening 
to what must necessarily be but an imperfect sketch of an interest- 
ing and important subject. 
IV. 
rUETHER NOTES ON COAST INSECTS FOUND AT 
BRANDON. 
By C. G. Barrett. 
Head 28ih Novemher, 1871. 
It will be remembered that I brought forward last year some facts 
respecting the occurrence of certain species of coast insects on the 
“ Breck” sand, (of which the district round Thetford and Brandon 
is composed) which facts seemed to me to lead strongly to the 
conclusion that these species had occupied this district from the 
time when it was a part of the tlien sea-coast. Besides recording 
the species wliich had come under my own observation, I men- 
tioned certain other species — Acjroiis vull!(jcm and cursoria among 
them — which have been found in this country exclusively attached 
to coast sands, and that it would be interesting to ascertain whether 
they Avcre also to be found in the same district, In a subsequent 
* Sir W. Jones informs me of the formation of several pits on his 
estate brought about in tliis manner. 
