THE FARMER AT HOME. 423 



the natural and necessary result of its rotation on its axis. But in 

 order that it might yield to the force resulting from such a motion, the 

 matter of which it is composed must have been soft. Now, although 

 water is capable of being compressed, and so far as we can judge, of 

 taking any degree of density, according to the force exerted upon it, 

 still the shape of the earth is not that which would have resulted from 

 such a mass of water. There may be particular portions of the sea 

 that extend to the depth of several miles, as there are particular points 

 of the solid crust of continents, that rise to this height above the 

 general level. Still we havo reason to believe, that the average depth 

 of the ocean does not much exceed three thousand feet. 



It is thought that heat may have been the original cause of the 

 fluidity of the earth, and that there may still remain enough to keep 

 the interior portions in the same state. The more the subject has been 

 examined, the more the evidence has accumulated in favor of the po- 

 sition that the temperature increases as we descend below the surface. 

 There are numerous instances in which we have been able, by means 

 of natural or artificial excavations, to penetrate to the depth of from 

 thirteen to sixteen hundred feet. The general inference from all the 

 observations made in different parts of the earth is, that there is an 

 increase of heat amounting to about one degree of Fahrenheit for 

 every forty- six feet in depth ; that at the depth of ten thousand feet, 

 the heat would be sufficient to boil water, and that at the depth of 

 about one hundred miles, or one fortieth part of the distance to the 

 centre, the heat would be intense enough to melt most of the earths 

 and stones that are known to enter into the composition of the globe. 

 These facts and inferences have an important bearing upon the phe- 

 nomena of earthquakes and volcanoes, and open a wide field of specu- 

 lation to the natural historian and geologist. 



THERMOMETER CHUKJST. This chum has been so con- 

 structed that the cream or milk is readily brought to the desired tem- 

 perature without mixing water or other substances, and the tempera- 

 ture certainly and definitely determined, which proves invaluable in 

 the art of making butter. One improvement consists in the construc- 

 tion of a double bottom made in the form of a semicircle, of two 

 sheets of zinc, or other metal, placed one above the other, the cream 

 to rest upon the uppermost. Between the two sheets forming the 

 bottom is a space, or chamber, into which may be introduced cold or 

 warm water, as may be required to increase or diminish the temper- 

 ature of the cream or milk. The water is easily applied by means of 

 a common tunnel, through an aperture or hole in the side of the 

 churn. 



Another improvement is a thermometer permanently placed in 

 one end of the churn, entirely secure from breaking or accident, 

 marked at sixty-two degrees, and which is always visible, so that the 

 operator may know and determine with certainty when the cream or 



