XIX.] CANADA ROCK ELM. 177 



be taken as indicating a deterioratioa which will affect 

 its strength and durability. 



The United States Ash is much slower in growth 

 than the English, and is probably not so durable. 



There are several other species of Ash in Canada 

 and the United States, but none are of much importance 

 as timber. 



CANADA ROCK ELM (Ulmus Americana) 



is found growing abundantly in the low woods of North 

 America, from New England to the Carolinas. It at- 

 tains moderate dimensions, with a clean straight stem, and 

 few heavy branches, and yields timber for the market 

 in logs of from 20 to 40 feet in length and from 11 

 to 16 inches square. 



The wood is whitish-brown in colour, hard, tough, 

 and flexible, with a fine, smooth, close, silky grain; 

 and as it has only a small quantity of sap-wood it can 

 be worked up closely and economically. It is necessary, 

 however, to remove the sap in the conversion of the log, 

 as, unlike that of the English Elm, it is of a perishable 

 character. ' 



Rock Elm used to be often substituted for the English 

 common Elm for garboards and planking in ship-building, 

 as it is very durable when employed under water; it 

 is also used for ladder steps, gratings, &c., on account 

 of its clean whitish appearance ; and owing to its flexible 

 character it is frequently used in boat-building. It 

 cannot, however, be used with advantage in bulk, or 

 even in plank, if exposed to a dry current of air, as 

 under such circumstances it is very liable to split with 

 fine deep shakes from the surface. 



Having this serious liability to rend in seasoning, 



N 



