434 



Transactions of the Canadian Institute. 



[Vol. VII. 



effects by laboratory experiments alone, then the prohibitory legislation 

 needs no better defence. 



Without anticipating further the results of these experiments, I 

 shall proceed to describe them, so that the reader may be in a position 

 to draw his own conclusions, if he differs from mine. 



The Sinking of Sawdust. 



As regards the sinking of sawdust, the following experiment was 

 typical of a large number which were carried out, in order to determine 

 how much and how quickly sawdust sank after being thrown into the 

 water at the tail end of a mill. 



A litre measure was filled up to 900 c.c. with tap water, and then 

 100 c.c. of moderately packed pine sawdust was poured upon the water. 

 The moment the sawdust touched the surface, particles began falling to 

 the bottom, and continued to fall for nearly twenty minutes. During this 

 time the water had penetrated 100 c.c. of the floating sawdust, and this 

 volume of it be;;Tan to sink very slowly en masse. Figure i represents 



the conditions in the experiment at the 

 end of the 20 minutes. No less than 

 70 c.c. of the sawdust lay at the bottom ; 

 100 c.c. were between the 700 and 800 

 marks, and about 20 c.c. only were float- 

 ing. The 100 c.c. of sawdust at the 

 beginning of the experiment had swollen 

 to nearly 200 c.c. On giving the vessel 

 a slight tap, the 100 c.c. of water-logged 

 sawdust, lying between the 700 and 800 

 c.c. marks, suddenly upset and most of it 

 sank to the bottom. The large parti- 

 cles, however, rose again to the top, so 

 that in less than three minutes more, only 

 30 c.c. were floating, and the rest, swollen 

 to 170 c.c, were lying at the bottom. 



Sawdust floating^ 

 20 c.c. 



Sawdust sinking- 

 100 c.c. 



■A\'>'^'! ... . 



800 c.c. 



70 c.c. 

 Sawdust sunk 



The following conclusions are based 

 FIG. I. upon the results of many similar experi- 



Litre measure at end of 20 minutes. ments : FrOm 5O per Cent. tO 80 per 



cent, of white pine sawdust sinks in 

 standing water, in from two to three minutes. The variations in quantity 

 and time depend upon, (i) the size of the particles (2) upon the manner 



