1883.] NATURAL SCIENCES OF PHILADELPHIA. 201 



the average per annum, a tree of thirty-three feet diameter would 

 give 2376 years old, which is about the same as given by an actual 

 count of rings. At Harrisburg or Juneau, in lat. 58°, a Sitka 

 spruce (Abieii Sitkensis) cut down, gave 149 rings from centre to 

 circumference — 298 lines, in a trunk three feet across. This 

 gave an average of about eight to an inch in this 149 years old, 

 three feet tree. At Wrangel, lat. 56°30', a tree of the western 

 hemlock {Abies Merlensiana) which had been blown down, and 

 afterwards divided by a cross-cut saw at four feet from its base, 

 gave eighteen lines to an inch, and the annual growths seemed 

 ver}^ regular almost to the centre of the tree. It was six feet in 

 diameter, and must have been a grand old tree in its day. It had 

 evidently been broken off years before it was blown down, but 

 the length of this trunk up to where it had been broken was 132 

 feet, and four feet in diameter at that height. But allowing as 

 much as twelve to an inch, it would give for the point cut across, 

 six feet, an age of 432 years. At Kaigan Harbor, lat. 55°, the 

 Sitka spruces were very large, and of great height. He measured two 

 of the largest, which were twenty -one feet in circumference each. 

 Allowing eight to the inch, as in the tree of the same species at 

 Harrisburg, it gives 336 years as the age of the tree ; so far as 

 appearances went, these trees were in the height of vigor, and 

 there seemed no reason, judging from experience in other cases, 

 why these trees might not flourish for a hundred years yet. Mr. 

 Meehan had no doubt that these trees in these latitudes in Alaska, 

 would easily have a life of 500 3^ears. 



Turning now to the Atlantic States, we find 200 years as 

 the full average term of life for its forest trees,- with the excep- 

 tion, perhaps, of the plane, Plalanits occidentalism which is the 

 longest lived of all. Trees famous for longevity in Europe are 

 comparatively short-lived here. In the old Bartram Garden, 

 near Philadelphia, where the trees can be little more than 150' 

 years old, nearly all are past their best. The English oak,. 

 Quercus Robur^ which in England is said to live for a thousand 

 years, has grown to full size and wholly died away in this garden,, 

 and the foreign spruces are on the down grade. The great 

 cypress, Taxodium distichum, which must have made an average 

 growth of four lines a year, has also begun to show signs of 

 deterioration. Silver firs, Abies pectinata^ in the vicinity of 

 Philadelphia, known to be planted in 1800, are decaj'ing. This is 

 the general experience. 



In seeking for the cause of this difference, we are accustomed 

 to look at the relative humidity of the atmospheres of Great 

 Britain and the Atlantic United States. Evergreens like Cerasus 

 Laurocerasus^ Laurus nobilis^ and Viburnum tinus, which will 

 endure a temperature of 25° below freezing point in Great 

 Britain, are killed by 10° in Philadelphia; and it is believed 

 by the dryer atmosphere causing a heavier drain for moisture on 

 the vital powers of the plant to supply. A strain which will 

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