B. TERRESTRIAL PHYSICS AND METEOROLOGY. Ill 

 

 tables for computing relative humidity are applicable only 

 for stations at or near the sea-level, or else they neglect to 

 make the necessary correction for altitude, owing to the 

 labor of the computation. The table given by Hatier is per- 

 fectly general in its applicability, and enables one to com- 

 pute the relative humidity, no matter what the barometric 

 pressure may be, and is worthy the adoption of American 

 observers. Res. Obs. du Pic dii 3Iidi, p. 21. 



IMPROVEMENT IN ANEROIDS. 



Hon. Ralph Abercrombie notes that a decided improve- 

 ment in aneroid barometers consists in jeweling the ends of 

 the arbor of the index hand like the ordinary pivots of a 

 watch, and making the hands work underneath the cap, in- 

 stead of in the usual manner. He recommends conical piv- 

 ots as preferable to straight ones. Quar. Jour. Brit. Met. 

 Soc. 1876, 87. 



THE CLIMATE AND TREES OF SACRAMENTO BAY. 



An interestino; memoir on the distribution of forests and 

 trees in the neighborhood of San Francisco is given by Dr. 

 Cooper in the fifth volume of the Proceedings of the Cali- 

 fornia Academy. He states that the most notable fact in 

 botanical geography is the comparative scarcity of trees as 

 compared with regions to the northward or southward, 

 and, after a careful study of the subject, he concludes that 

 the chief cause of this deficiency is the prevalence of strong 

 winds, which throughout the dry season blow so steadily 

 into the Golden Gate from the northwest, and are drawn by 

 the ascent of hot currents far into the interior, following, 

 generally, the course of the valleys upward from the bay of 

 Sacramento. Where the west winds blow with sufiicient 

 force, the tree growth is limited to scattered groups on the 

 eastern slopes of the hills. Elevation above the sea has less 

 effect than w^ould be expected. Trees that are fully devel- 

 oped in unexposed regions dwindle into shrubs in the ex- 

 posed portions, assuming the aspect of trees stunted by the 

 cold, as on mountain summits. Dryness, however, is still 

 more influential than cold. The general course of tlie 

 mountain ranges is nearly northwest. Tlie ^vind strikes the 

 southwest slopes obliquely, and the sun shines on the same 



