225 [Jackson. 



hence all the tropical fruits abound there. The next stopping place 

 was Mansanilla, which is the place of export for the silver from the 

 Zacatecas and other silver mines of Mexico at the present time. Many 

 millions of dollars' worth of silver in the form of bricks, are exported 

 from that place. While in Mansanilla harbor Dr. Jackson had an 

 opportunity of studying the habits of the large and voracious sharks 

 which were very numerous. It is commonly believed that sharks turn 

 over, bringing their mouths up under an object floating on the water 

 when they seize it, but he observed, when the intestines of oxen were 

 thrown over, that the sharks after playing around this food for at least 

 five minutes, swimming cautiously all around it and viewing it care- 

 fully, finally darted suddenly at it and thrusting the nose out of the 

 water and over the food, seized it, and never in any case turned over 

 in the manner they have been supposed to do. The natives swim in 

 the water while sharks are near, and do not seem to fear them, but they 

 do not go so far from their boats as to prevent their returning to them 

 if they see a shark has any intention of making an attack, and there 

 is always time enough to escape, since the shark is so very cautious. 



Amved at San Francisco April 7th, he entered the harbor amid a 

 heavy shower, which was the last rain of the season ; and not a 

 drop of water fell in California for four months afterwards. The dry 

 season (our summer,) is the winter of California ; drought takes the 

 place of and is equivalent to, the cold of winter, giving to the vegeta- 

 tion a period of rest. Owing to the uniform north and north-westerly 

 winds, which blow over San Francisco from Russian America during 

 the dry season, the temperature of the place is generally from G0° to 

 65° F. during that season, and the current of cold water from the 

 north setting into the bay of San Francisco adds to the coolness of the 

 climate. From the name. Golden Gate, one is apt to form a brilliant 

 conception of the entrance to the harbor of San Francisco, but it is 

 really a dreary and chilly spot, remarkable chiefly for its cold fogs and 

 innumerable sea lions. 



After a few days' rest in San Francisco, Dr. Jackson, with three 

 gentlemen from Boston, proceeded to the State of ^Kevada, examining 

 on their Avay the celebrated gold mines (auriferous quartz veins) of 

 Amidor County, California. The Sierra Xevada range of mountains, 

 white with snow, with its serrated peaks, fully justifies the Spanish de- 

 scriptive name which signifies a Saw of Snow. By the Placerville 

 route the Sierra range was crossed at an elevation of 7,467 feet above 

 tide water, sledges being substituted for wagons, the snow being about 

 ten feet deep on the road. After crossing the mountains we descend 

 into the mountain valley of Washoe mines district, and reach Virginia 

 City, which is elevated 6,342 feet above the sea and is surrounded by 



PROCEEDINGS B. S. N. H.— VOL, X. 15 APRIL, 18G6. 



