ACADEMY OF NATURAL SCIENCES. 327 



we have everywhere on this coast observed, to suppose that the limit to which 

 arboreal growth reaches, should cot fall considerably in going north three hund- 

 red miles, rather than rise 1,000 feet, as would be the case if Mr. Wood's meas- 

 urements were correct. Finally, that Mr. Wood's figures are not very reliable 

 is shown by the fact, that on plotting his estimates of distances traveled and 

 the angles of the slopes as given by him, it was found that, to correspond with 

 his statements, the mountain must be no less than 33,400 feet high. 



Finally, Professor Whitney concluded that we have as yet no satisfactory 

 evidence to invalidate the statement previously made by him, that we have in 

 California the highest mountains in the United States, and the grandest and 

 largest mountain mass iit North America, although one or two of the volcanic 

 cones of Mexico rise to higher altitudes than any of our peaks. 



Prof. Whitney also exhibited one of the short barometers made 

 for the Geological Survey, by James Green, of New York. Hav- 

 ing had occasion to work at high elevations — the party being some- 

 times, for weeks together, camped at from 8,000 to 10,000 feet 

 above the sea — it has been found that the vacuum in the ordinary 

 barometer tubes soon becomes deteriorated, and the mercury dirty 

 from the constant lowering and raising of the column, which is re- 

 quired when a large number of observations are taken at so great 

 an elevation. By having the barometer tube made only long enough 

 to commence the reading at about twenty-four inches, or at an ele- 

 vation of 6,000 or 7,000 feet, the difficulty above specified is to a 

 great degree avoided, and the instrument made much more porta- 

 ble and convenient to carry, especially on peaks so steep that both 

 hands are needed to aid in climbing. Two of these short barome- 

 ters have been used in the high mountain work of the California 

 Survey, and found extremely convenient. Of course the short ba- 

 rometer must be compared with a long one at some station camp of 

 sufficiently great elevation to allow this to be done. 



Dr. Gibbons made some remarks on the inferior quality of the 

 macadamizing material employed in this city. He inquired if any 

 person knew of the existence of any better stone for this purpose, 

 in the vicinity of San Francisco. Prof. Whitney replied that an 

 excellent basaltic rock was to be had in great abundance near Pet- 

 aluma, at a point convenient for shipment, and that there was no 

 really valuable rock for macadamizing to be had nearer than this 

 point. 



