200 PROCEEDINGS OF THE ACADEMY OF [1883. 



groups of a formation are almost as definitel}^ marked off in the 

 same order, the world over, as are the formations themselves. 

 After breaks in formations the appearance of characteristic fossils 

 is largely the same ; whereas, on the theory of synchronism of 

 distinct faunas, such a succession of forms would certainl}^ not be 

 constant. After deducing further evidence from the lithological 

 characters of the rock-masses of the various geological formations, 

 the speaker maintained that the views entertained on the subject 

 by the older geologists were more probably the correct ones, 

 namely : that formations characterized by the same or very 

 nearly related faunas in widely separated regions belonged, in 

 very modei'ate limits, to approximately the same actual age, and 

 were, to all intents and purposes, synchronous or contem- 

 poraneous. 



Longevity of Trees. — At the meeting of the Botanical Section, 

 October 8, Mr. Thomas Meehan remarked that there was nothing 

 phenomenal in the great age of the mammoth sequoias, as other 

 trees on the Pacific coast exhibited great age. In order to ascer- 

 tain whetlier more than one annual circle of wood is formed in 

 each year, he tested the matter in various ways. For instance, a 

 pine or spruce would be found to make an average growth of a 

 foot a year up to fifteen j^ears old ; from that to about thirt}"^ 

 years, nine inches ; from that on, six inches ; after that a stage 

 was reached where the erect growth ceased to any considerable 

 extent, and the growth force seemed turned toward the lateral 

 branches. In the pine forests of the Pacific coast, there was no 

 danger of error in fixing the age of the average tree of 'sixty feet 

 high, at about fifty years. Wherever such a tree was cut down, 

 and an opportunity afforded to count the circles, they would be 

 found to correspond so nearl}^ with the calculated age, as to 

 prove that it was quite safe to assume a single circle for a single 

 year. Then there was a remarkable degree of uniformity in the 

 diameter of these annual growths in most trees, so that when 

 once we had the number of the circular lines to an inch, and the 

 diameter of the tree, we could tell its age near enough for general 

 purposes. In some pine trees growing on ver>- rich soil, he had 

 found as few as about four circles to an inch. For instance, a section 

 of a Finns Lambertiana (in Mariposa), four feet across, had but 

 189 circles ; but here the increased size of the trees corresponds 

 with the larger annual circles. Trees of this species of pine here 

 were not uncommon, measuring tliirt}^ and a few thirty -three feet 

 around. No matter, however, how vigorous may be the growth of 

 trees under fifty or one hundred years, they decrease with age, and 

 we may safely allow six rings to an inch in these older sugar pines, 

 which would make the thirty-three feet tree 396 years old. The 

 outer growths of sequoia were ver^- narrow. He counted as many 

 as eighteen to the inch, while the rings in the interior of cross- 

 sections would show about six to the inch. Allowing twelve as 



