158 MADRAS FISHERIES BULLETIN [VOL. XVI, 



The four boats having each performed a complete circuit are 

 next ranged in line abreast in the same manner as before, between 

 the quarter and the half mile buoy and each makes a second circuit. 

 The day's work is completed by a third and last circle, in this case 

 between the buoys distant respectively half mile and three-fourth 

 mile from the ship. 



The four boats make a total of twelve concentric circuits, each 

 boat making three. The results shown upon the coxswains' 

 diagrams — each of which has three concentric circles drawn upon 

 it representing the three circular paths covered — are transferred 

 by the inspector to a final diagram or plan furnished with twelve 

 concentric circles. When this has been done the distribution of 

 old and of young oysters is graphically shown for a circular area 

 having a diameter of a mile and a half. 



After calculating in square yards the area occupied by oysters, 

 the approximate number thereon may be estimated by taking the 

 average number of oysters per dive (ascertained by scrutiny of the 

 divers' results) in conjunction with the average amount of ground 

 which a diver is credited with being able to clear at one descent. 

 Usually this area is considered on average ground to be from two 

 and a half to three square yards. By assuming the area per dive 

 to be three square yards the clanger of an overestimate is avoided. 



(c) Purchase or charter of an inspection depot ship. — To carry out 

 inspection satisfactorily I recommend that either a schooner be 

 built, purchased, or chartered, to serve as the headquarters or depot 

 upon which the inspection staff of divers and boatmen may live. 



If purchased or built specially, the latter of which would be the 

 more economical and satisfactory plan in the long run, cooler and 

 more commodious quarters could be fitted up than upon a steamer, 

 and being wooden there would be practically no liability to error 

 in the accurate taking of compass bearings. 



A steam vessel would be required for towing purposes. The 

 " Margarita " might be used for the present and when it becomes 

 necessary to replace her, the next vessel should be a screw steamer 

 built and fitted specially for dredging and towing so that when not 

 engaged in the latter duty, she might be used for the dredging 

 either of chanks or of fishabie oysters for market and for valuation 



sample. 



Meanwhile the "Margarita" should be altered and fitted to 

 serve dredging purposes for which she is by no means unsuited. 



