1902-3.] Sawdust and Fish Life. 435 



in which they are made, (3) upon whether the water is perfectly still 

 or agitated, and (4) upon whether the particles are dry or moist. 



Large particles sink much more slowly than small ones, because the 

 latter are more easily penetrated through and through by the water. 



Dust made with a hand-saw sinks more slowly than sawdust made 

 with a large mill saw. The difference seems to be due to the difference 

 in the force with which each is made. A large upright or circular lum- 

 ber saw strikes the log with great force, squeezes out the imprisoned air 

 from the wood fibres, renders them denser, and as a consequence they 

 sink more quickly than particles of a similar or smaller kind which have 

 been made by a hand-saw. 



When water is slightly agitated, sawdust thrown upon it sinks more 

 quickly than when the water is perfectly still. Consequently, in the 

 swells of a steamer, in the waves made by wind, and in the ripple of a 

 slight rapids, all the sawdust excepting the largest particles would sink 

 to the bottom in a k\v minutes. 



If thrown into a rapidly flowing stream, sawdust is carried down- 

 wards until it reaches comparatively still water, and then the finer 

 particles sink ; the coarser may be carried for miles and miles down a 

 river and out into the bays of a lake or sea. 



In laboratory experiments the coarser particles would float for 

 days, because the water is unable to penetrate the fibre and displace the 

 imprisoned air, which gives to wood its buoyancy. Wood fibre is, of 

 course, heavier than water, and therefore sinks ; and pine logs would 

 sink much more quickly than they do only that the water cannot pene- 

 trate their interstices and drive out the air. Yet they do sink in con- 

 siderable numbers, as every lumberman knows. 



Hardwood logs cannot be floated to market at all, because the 

 water of the cell-sap permeates them, rendering them heavier than 

 water and they sink. A very simple experiment illustrates how pine 

 logs sink after being in the water some time. Throw a piece of black- 

 board crayon into a dish of water. At first it floats, but soon bubbles 

 of air escape from the chalk, and in a few moments it sinks to the bot- 

 tom. So is it with sawdust and logs. 



Sawdust from cedar takes a longer time to sink than that from 

 pine. In fifteen minutes 66 per cent, only had sunk, probably because 

 it contains more resin and consequently water-logs more slowly. Maple 



