118 JOURNAL OF THE PLYMOUTH INSTITUTION. 
Many houses in Emma Place, &c. use the cavern there as a cess-pit, 
a highly dangerous experiment for the locality. Little danger 
would be apprehended if these discharges found their way directly 
to the wells ; for then the high road to the sea would have been 
reached. Injecting refuse into a limestone cavern, over which 
stand houses, irrespective of the water communication, is a reckless 
proceeding. In these caves the temperature is often several degrees 
higher than the atmosphere, as may be verified by a visit to 
Oreston quarries on a cold, sharp day, where a volume of vapour 
is seen rising from the mouth of a cave exposed in the government 
quarries. The temperature is at once felt by the hand to be higher 
than the outside atmosphere. These are just the conditions for 
decomposition of the sewage matter injected, while the spacious 
cavern forms a commodious gasholder or accumulator, dependent 
either on the atmosphere or the tidal waters for its discharge. 
