22 Mr Stevenson on the Building Materials 



when this cannot be done, they continue their perilous voyage 

 in the dark, exhibiting hghts at each corner of the raft to 

 warn vessels of their approach to them. The St Lawrence 

 rafts vary from 40,000 to 300,000 square feet, or from about 

 one to no less than seven acres in surface, and some of them 

 contain as much as L.5000 worth of timber. If not ma- 

 naged with great skill, these unwieldy specimens of naval 

 architecture are apt to go to pieces in descending the rapids, 

 and it not imfrequently happens that the labour of one, and 

 sometimes two seasons is in this way lost in a moment. An 

 old and experienced raftsman, with whom I had some conver- 

 sation on board of one of the St Lawrence steamers, informed 

 me that he, on one occasion, lost L.2500 by one raft which 

 grounded in descending a rapid and broke up. He said the 

 safest size for a raft was from 40,000 to 50,000 square feet, or 

 about one acre, and that five men were required to work a 

 raft of that size. 



The species of forest trees indigenous to different countries 

 is an interesting subject connected with vegetable physiology. 

 There are said to be about thirty forest trees indigenous to 

 Great Britain, which attain the height of thirty feet ; and in 

 France there are about the same number. But according to 

 the best authorities, there are no less than 140 species which 

 attain a similar height indigenous to the United States. 



To notice each of these numerous species, whose timber is 

 employed by the Americans in the arts, even if I were able to 

 do so, would greatly exceed the limits to which I am restricted 

 by the nature of the present communication, and I shall there- 

 fore only make a few remarks regarding those timbers which 

 are most highly prized and most extensively used in the ship 

 carpentry and public works of the country. 



The first which I shall notice is the Live Oak {Quercm vivens)\ 

 so named because it is an evergreen, its leaves lasting during 

 several years and being partially renewed every spring. It 

 grows only in the southern states, and is one of the most 

 valuable of the American timbers. The duty imposed by our 

 government on wood from the United States, prevents its im- 

 portation into Britain, and as live oak grows only in the 

 LTnited State*« and is not found in Canada, it consequently 



