4Q0 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747-8. 



before mentioned, and ia man that he had heard of, were both dead ; and since 

 gentian is of general use in medical compositions, as well as the primary ingre- 

 dient in the cordial hitters ladies make for their own use. 



Of Large. Subterraneous Caverns in the Chalk Hills near Norwich. By Mr. 

 ffm. Jrderon, F.R.S. N" 486, p. 244. 



About: a quarter of a mile from the city of Norwich, on the east side, and 

 near the entrance of Moushold-heath, is a large subterraneous cavern, which 

 has been formed in a long series of time, by digging out chalk for making lime. 

 There is only one entrance into it, about 1 yards wide, and nearly the same height ; 

 however the height gradually rises, till at last it measures in some places from 1 2 to 

 14 yards. But though the entrance is so small, the whole area within is of such a 

 large extent, that 20,000 men might with great ease be placed in it, and from the 

 entrance to the farthest part of these cells, measures full 400 yards ; and these 

 passages are often 10 or 12 yards wide, with branchings out on the sides, into 

 various lanes and labyrinth-kind of windings, which every now and then open 

 into each other ; which renders it no easy task to find the way out, when a per- 

 son has been a little bewildered in these subterraneous mazes. 



Most of these vaults are arched at top, by which the immense weight above is 

 well supported ; a weight no less than that of hills, whose perpendicular altitude 

 above the tops of these arches is 20 or 30 yards, if not much more. 



How deep or thick these rocks of chalk are, no one can tell ; for in sinking 

 the lowest wells, they have never been dug through ; and consequently must be 

 exceedingly deep. The chalk at the farther end of this caveni is so very soft, 

 that it may be moulded with the hand like paste ; which is probably its original 

 consistence, and what it always retains, till it becomes exposed to the air. In 

 the very lowest parts of these vaults Mr. A. has picked up several kinds of fos- 

 sils, figuretl by marine bodies ; such as echini, pectunculi, common or fluted 

 cockle, belemnitae, &c. Sounds made beneath these arched roofs are strongly 

 reflected from side to side ; so that the least whisper may be heard at a consi- 

 derable distance. The beat of a pocket-watch was heard distinctly full 20 yards 

 from where it was placed. 



He visited this place on the 1st day of November last, to try the temperature 

 as to heat and cold ; and carried with him a thermometer regulated by one of 

 Mr. Hauksbee's, which he set down at the farther end of these caverns ; and 

 letting it remain there for some time, he found the mercury rested at 52°; which 

 comparing with the register he had kept, was within half a degree of a medium 

 between the greatest heat and the sharpest cold known in that city for 10 years 

 past ; and it is very probable, if the 2 extremes had been taken more exactly, 

 the temperature in these caverns would be found to come yet nearer to the me 



