OBSERVATION'S ON THE PLANKTON OF LOOE POOL. 329 



to store in an outhouse near the pool the usual pai^aphernalia 

 necessary for biological investigation. 



Although there does not appear to be any record of the 

 Looe Pool having ever been used for purposes of navigation, yet 

 there is no doubt that, speaking geologically, it was once a natural 

 indentation of the coast, into which the tide flowed twice daily 5 

 and that an estuary extended up the Looe valley as far as the 

 rising ground on which the town of Helston now stands. There 

 are several similar estuaries along the shores of Devon and 

 Cornwall at the present day. Now, as we have seen, the lower 

 portion of this estuary is converted into a fresh- water lake ; while 

 a picturesque stream, fringed with rushes, meanders slowly along 

 the centre of the Looe valley, and ends in a marshy delta at the 

 north-eastern extremity of the pool. 



Until quite recently, and especially after a heavy rainfall, 

 the amount of water in the pool and valley occasionally increased 

 to such a degree as to inundate the houses in the lower part of 

 Helston. On these occasions a quaint ceremony would take 

 place. The occupants of the houses that were inundated would 

 proceed in a body to the residence of the owner of the pool and 

 present him with a leathern purse containing three half -pence. 

 The owner, on receiving this present, would give the deputation 

 permission to cut a channel through the bar, and allow the pent- 

 up waters to escape. The out-flow of water through this newly- 

 cut channel, once commenced, soon became a rushing torrent ; and 

 the sea in Mou.nt's Bay for some miles distant from land would 

 become discoloured. This channel would remain open and allow 

 the entrance of sea-water into the pool twice daily for a long or 

 short period according to the direction and force of the wind. A 

 fresh gale from any point of the compass between south and 

 west would soon close this passage ; but while the wind blew from 

 any other quarter it would remain open. Now, the amount of 

 water in the pool is regulated by sluices ; a large adit, to allow 

 the escape of surplus water being located in the south-western 

 corner. 



Early in the year 1837 a very accurate survey of the pool 

 was made under the auspices of the distinguished engineer J. M. 

 Eendel, with the view of making a harbour in Mount's Bay ; 



