SPECIFIC WEIGHT. 59 



naturally in the warmer climates are, on the whole, heavier 

 than those from cooler regions, e.g., heavy tropical iron woods 

 when compared with European oakwood. However, it must 

 not he ignored that some tropical woods are extremely low in 

 the scale of sp. weight. The variations in the weight of woods 

 of the same genus, but of different species and heat require- 

 ments, are less decided. Europe is so poor in species of the 

 same genus of trees, as to afford few examples of this. In 

 North America, the white oak when grown in the more southern 

 States has an average sp. w r eight of 89, the black oak that of 

 73; the same oaks when grown in northern States have sp. 

 weights of 77 and 70 respectively.* So far as our experience 

 goes, however, different species of a genus that have identical 

 heat requirements, or are cultivated in similar climatic regions, 

 do not produce wo<>d differing in sp. weight or in other quali- 

 ties. On the contrary, it appears that nearly related species 

 of trees, c.rf., Sitka and Norway spruce, Nonlimum's and our 

 own silver-fir, the \\liite American and our sessile oak, sugar- 

 maple and sycamore, etc., produce equally heavy wood, if 

 grown under conditions that produce heavy wood for the 

 genus in Europe, or e<juali\ light wood when under opposite 

 conditions. 



Attention is here directed to some common errors made in 

 comparing exotic and indigenous plants. Equally favourable 

 conditions of soil and climate should be presupposed. 



Exotic conifers when introduced into European lowlands 

 should not be compared as regards the quality of their wood 

 with our own conifers grown in I, but with them when grown 

 also in the lowlands. Thus Japanese larch planted in our 

 lowlands should be compared with lowland and not mountain 

 European larch. 



A.8 an instance of a second error, Weymouth pinewood was 

 formerly considered the best pinewood of North America, 

 because it afforded the longest, strongest, and most work- 

 able pinewood from the earlier settlements in the north-east 

 of America. In Europe there are many better conifers, so 

 that the American preference for it counts for nothing with us. 

 The Americans have misjudged similarly the quality of the 



* Census Report oE the United States, 18HO. 



