60 W. B. Jillson — Recent Volcanic Eruption. 



score or more of standiDg and fallen logs. The abundance of 

 casts is a measure of the protection from the destructive force 

 of the two main flows. 



The occurrence of this small locality has not been mentioned 

 before in the literature of the subject, although a number of 

 other more conspicuous places adjacent to the main trails have 

 been described. The vertical casts appear like man-holes in the 

 lava floor, '^ the wells in lava " of Elliott.* At depths of from 

 nine to twelve feet these regularly outlined cylindrical carbon- 

 ized casts of the trees extend outwards and downwards into 

 giant root casts. The horizontal casts appear as long, regu- 

 larly cylindrical lava-moulds extending back considerable but 

 undetermined distances into the rock. The horizontal casts 

 are in general of a uniform size and from two to three feet in 

 diameter. The vertical trunk or stump casts seem to be larger 

 (which we should logically expect), some of them attaining 

 five feet in diameter. 



The museum specimen (flg. 1) was taken from one of the 

 horizontal casts of this area. It shows in fine relief the longi- 

 tudinal breaking or splitting of the wood, and the transverse 

 or circumferential check rings, both of which are due to the 

 special kind of carbonization and rapid contraction of the 

 wood cells which the tree trunk underwent in its nearly-closed 

 lava kiln. The fine longitudinal striae-casts show the character 

 of the annual growth layers of the wood. The size and rough 

 character of the largest ridges on the cast indicate that the log 

 had been greatly charred before the lava struck it. Studies of 

 the carbonization of the cast have led to the placing of the 

 cast-producing tree in the conifer group. This statement finds 

 strong support in the great diameter of the casts themselves. 

 The size of these trees is indicated by the flatness of the arch of 

 the section of the lava cast shown in flg. 1. 



The important bearing of these tree casts upon the determi- 

 nation of the dates of various flows is pointed out by Diller,f 

 who also gives a resume of the better known literature of the 

 subject. He publishes a letter from Mr. F. Y. Coville of the 

 Department of Agriculture, who while studying the flora of 

 Mt. St. Helens found some interesting charred trees under 

 recent gravels of the Kalama River. The following statements 

 occur in the second paragraph of Mr. Coville's letter : " The 

 character of the charcoal, which need not be described in 

 detail here, is such as at first to suggest that it was made in a 

 very carefully prepared kiln. There are, however, no char- 

 coal pits in the region. ... It is evident from the peculiarities 



* Elliott, C. P., Nat. Geog. Mag., vol. viii, p. 227, 1897. 

 f Diller, J. S., Latest Volcanic Eruptions of the Pacific Coast, Science, 

 N. S., vol. ix, pp. 639-40, 1899. 



