4i 



watchers to move freely in their boats from valle to valle. 

 Accordingly we find at almost every fishing station, a 

 narrow service-canal passing round at one side giving 

 access to the valle from the feeder canal from the sea. In 

 other places a similar narrow boat canal cuts the separat- 

 ing embankment between adjoining valli. To prevent the 

 escape offish by way of these service-canals, wooden locks 

 of the simplest description are installed in convenient 

 positions in their course. Figure 12, pi. VII., depicts 

 clearly the appearance and arrangement of one of these 

 locks. The lock " gates " are stoutly built wooden 

 shutters extending the width of the cut, the ends and 

 lower edge fitting into wooden grooves in the wood 

 frame built into the bank and bottom of the channel. 

 The lower edge of the lock-shutter is shorter than the 

 upper to facilitate removal and replacement in the 

 retaining grooves. 



^.j!ii^LiL-.'^~ » 



Fig. 8. — Diagram of wooden shutter used as a lockgate on the 

 service-canal between a sea-canal and a valle. 



A, Handle by which it is pulled up when the lock is to be opened. 



Cycles of Bad Seasons ; Causes and Suggested 



Remedies. 



From time to time in spite of the great store of 

 empirical knowledge gained from centuries of struggle, 

 there occur disasters in this industry which impair its 

 prosperity for a series of years. During the past century 

 no less than six years are recorded as marked by exces- 

 sive Joss or mortality of fish, entailing a succession of 

 unremunerative fishing seasons varying in degree accord- 

 ing to the severity of the initial cause. It is probable, 

 I believe, for the reasons to be stated later, that these 

 cycles of disaster have tended to occur at shorter 

 intervals and with great intensity since the Mezzano was 



