PRACTICAL HINTS 



matter needs mentioning, it should be remarked that a hand-lens 

 should be used quite close to the eye, and the wood brought up 

 to it until it comes into focus. 



The weight per cubic foot is a detail which can nearly always 

 be ascertained by trimming and measuring the block, but if the 

 wood be not dry it should be put aside and weighed from time 

 to time until it ceases to diminish in weight. A rough method 

 of estimation is to plane or turn a stick truly parallel from end 

 to end, and to lower it gently by means of a thread into water 

 until the thread slackens (87). The point to which it sinks is 

 then marked and measured, and as the whole length of the stick 

 is to 62J (the weight of a cubic foot of water in lbs.) so is the 

 length of the wetted portion to the number of pounds per cubic 

 foot. If the figure 1000 be used instead of 62 J, then the apparent 

 specific gravity will be arrived at (1000 ounces =62 J lbs.). If 

 an irregular block be thrown into the water, a trained observer 

 can get very near to the weight per cubic foot by noting the 

 bulk submerged. These are not scientific methods, but they 

 are often useful when apparatus is not to hand. A better ex- 

 pedient is to employ a graduated glass filled to a certain height 

 with water, in which the wood can be immersed. The bulk 

 of water so displaced is a basis for working out the specific 

 gravity, except when the wood sinks entirely. It is not 

 possible to get rid of bubbles which buoy the wood up, or 

 to allow for the water the wood will absorb. The use of 

 Mercury gets rid of two of the objections, but not of that due 

 to the bubbles, besides which the wood has to be forcibly held 

 beneath the surface while the scale is read off. Hartig, I under- 

 stand, used a strong solution of Chloride of Lime and water, of 

 a given density, and so avoided all three difficulties, but a new 

 one was created by the salt which crystallised out on the fine fibres 

 of the wood and increased its apparent bulk. All my own weights 

 have been obtained by planing up the block quite truly, and 

 carefully measuring, but in no case do I give a less fraction 

 than i lb. per cubic foot, as this much variation can be observed 

 in specimens taken from different parts of the same tree. I 

 have added figures compiled from all possible sources, but 

 quote only those which stand for the maximum and minimum 

 recorded for the species. 



Smell and taste are not susceptible of measurement, and 

 can only be vaguely expressed by comparison with familiar 

 impressions. I have been accustomed to classify tastes as Sweet 

 (Pencil Cedar), insipid (Spruce), resinous (Pitch Pine), astringent 

 (Oak), bitter (Quassia), and nauseous (Sneeze wood). Scents I 

 have dealt with roughly in the same way, but each observer will 

 be forced to make a scale to suit himself. 



xxxvi 



