DURABILITY OF WOODS 169 



subsequent operation of pressure, 1 so that it was with some diffi- 

 culty that sections were made which would show structure. 

 The entire structure showed abundant fungus mycelia, while 

 the walls of the tracheids had suffered such reduction under the 

 operation of decay that the secondary walls were largely removed 

 with a corresponding obliteration of structural markings, and the 

 whole fabric was reduced to a compressed and greatly modified 

 skeleton consisting of the primary cell walls. Numerous speci- 

 mens from the Don valley show that while some are full of fun- 

 gus hyphae and present a correspondingly advanced state of decay, 

 others from precisely the same locality show a total absence of 

 all fungoid growths and a completeness of structural details 

 which leaves nothing to be desired by way of comparison with 

 recently cut material. Here it is still more evident that the 

 explanation applied to Picea nigra is not only applicable in this 

 case also, but that it affords a correct insight into the reason 

 for the various conditions of preservation of wood which, when 

 embedded in clay, is practically imperishable. A more recent 

 example of the larch may serve to lend emphasis to these con- 

 clusions, and it is of particular interest because it embodies the 

 changes which may arise in the course of practical use. In the 

 Peter Redpath Museum of McGill College there is a specimen 

 of an old aqueduct log which was laid down in the early days of 

 Montreal. The old and long-forgotten pipes were uncovered in 

 the course of excavations for a new water main on St. Paul 

 Street. They were about one foot in diameter, with a two-inch 

 bore. According to a communication in one of the daily papers, 

 the pipes were laid about eighty years previous, but were in 

 use for only a short time. An examination showed that when 

 the pipes were recovered they were practically sound, with the 

 exception of the superficial layers, which had so far yielded to 

 decay as to be in process of removal, and the external form had 

 thereby suffered some alteration. A microscopic examination 

 showed the structure to be so perfectly preserved as to admit of 



1 Recent studies indicate that the amount of pressure required to produce 

 such results need not be very great, probably less than one hundred pounds. 



