GEOLOGY. 295 



and about five days' journey from Goose Lake, there is a hill of pure 

 carbonate of magnesia, one hundred feet high. Much of it is per- 

 fectly white, while some is more or less discolored with iron, as if a 

 painter had been striving to give effect by a coloring of light and 

 shade. Large masses are easily detached, which, rolling down into 

 the river that washes its base, float off as light and buoyant as cork, 

 until they become saturated with water. A thousand wagons could 

 be loaded in a very short time, and there is enough to supply the 

 whole world. For three days' travel below, the soil seems to be im- 

 pregnated with it, and the banks of the river are formed of it." 



DISCOVERY OF PITCHSTONE ON LAKE SUPERIOR. 



DR. C. T. JACKSON read a description and analysis of pitch stone, 

 obtained by him at Isle Royal, Lake Superior, as follows : During the 

 summer of 1847, while engaged in the U. S. Geological Survey of the 

 mineral lands bordering upon Lake Superior, I discovered upon the 

 shores of Isle Royal some rounded pebbles and boulders of jet black 

 color, which appeared to be identical with pitchstone porphyry, like 

 that of the Isle of Arran, in Scotland. One of these pebbles, which 

 had been mislaid, I have found since I made my report to the govern- 

 ment, and have submitted it to chemical analysis, which has proved 

 my original opinion that it is pitchstone to be correct, and it has 

 since been confirmed by Mr. Tescheniacher. This mineral has not, so 

 far as I know, been discovered before in the L T nited States, and it may 

 therefore be interesting to mineralogists and geologists to know of its 

 occurrence on the shores of Isle Royal, in Lake Superior. I have not 

 had an opportunity of searching for the mineral in place, and it is 

 doubtful whether it occurs in the trap rocks which compose the prin- 

 cipal part of that island, or derives its origin from porphyry, erratic 

 boulders of which are so common in the drift and among the shore 

 pebbles of Lake Superior. Proc. Bos. Nat. Hist. Society. 



ON THE METEORIC MASS DISCOA'ERED AT SCHWETZ. 



M. G. ROSE gives to the Berlin Academy the following account of a 

 newly discovered meteoric mass: In the spring of 1850, while 

 removing a hill of sand, in the grading of a railway near Schwetz, on 

 the Vistula, a mass of iron, about four pounds in weight, was found at 

 a depth of four feet, at the limit where the upper sand covers the sub- 

 jacent clay. The mass sent to Prof. Rose is somewhat prismatic in 

 shape, about nine inches (Prussian) long, with the thickness of five 

 and a half and four inches, a line around it lengthwise being 24 inches 

 long, and transversely 17^ inches. The whole mass weighs about 43 

 pounds (livers). There is a fissure cutting it somewhat diagonally. 

 The outer surface is rounded and covered with hydra ted oxide of iron, 

 and so also that of the fissure. A surface cut and polished and acted 

 upon by an acid, exhibited fine Widmannstattian figures, much like 

 those of the Texas iron. There is a mixture of some large and small 

 grains of sulphuret of iron. M. Rose has detected in it nickel. 



