34 



contain the collector tiles is used. In Holland, in the 

 east arm of the river Scheldt, between ioand 15 millions 

 of limed tiles are laid down each year and the whole of 

 this number are simply piled on their edges, concave 

 surface downwards, in long parallel rows on the tidal 

 flats where the surface is stiff and well consolidated and 

 fairly free from the evils of soft mud and shifting sand. 

 At Arcachon conditions are not so favourable ; the best 

 situations there for spat collection are the abruptly 

 sloping margins of those flats in the central and eastern 

 sections of the basin washed by strong currents for a 

 certain period each tide and these places are almost all 

 characterised by a soft muddy surface a foot or more in 

 depth. These local conditions have two results, they 

 limit greatly the horizontal area available for spat 

 collection and they render necessary some device to 

 elevate the tile collectors above the mud. Vertical instead 

 of horizontal piling of tiles therefore takes place and to 

 permit of this being done economically and with safety 

 from the violence of wind, waves and currents, a crate- 

 like case of wood has been devised to contain the col- 

 lector tile. The tile-crate or r&che as it is called in France 

 from its resemblance when filled to honeycomb is made 

 of a size to contain one hundred tiles. The overall 

 dimensions of a ruche are 2 metres long, 60 cms. wide and 

 60 cms. high (6 \ ft. by 2 ft. by 2 ft.). The bottom frame 

 consists of four roughly sawn pine bars nailed together 

 with a single transverse strengthening batten at the 

 mid-length thus: — 



Fig. 3. — Bottom Frame of a Ruche. 



