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SCIENTIFIC SIDE-LIGHTS 



434 



surface of its summit, covered with loose 

 fragments, just below the level of which 

 glacier-marks come to an end, tells us that 

 it lifted its head alone above the desolate 

 waste of ice and snow. In this region, then, 

 the thickness of the sheet cannot have been 

 much less than six thousand feet, and this is 

 in keeping with the same kind of evidence 

 in other parts of the country; for, wherever 

 the mountains are much below six thousand 

 feet, the ice seems to have passed directly 

 over them, while the few peaks rising to 

 that height are left untouched. And while 

 we can thus sink our plummet from the 

 summit to the base of Mount Washington 

 and measure the thickness of the mass of 

 ice, we have a no less accurate indication of 

 its extension in the undulating line marking 

 the southern termination of the drift. 

 AGASSIZ Geological Sketches, ser. ii, p. 98. 

 (H. M. & Co., 1896.) 



2125. MEASURE OF THE POWER 

 OF HEAT It is singular how a modern 

 investigator will repeat an experiment that 

 dates almost from the dawn of human skill, 

 and discover a significance in it concealed 

 until the hour of his interrogation. Ages 

 ago the savage must have remarked that 

 the hard work of grinding and polishing 

 stone gave rise to heat. It remained for 

 James Prescott Joule, of Manchester, as re- 

 cently as 1843, to carry forward by a de- 

 cisive step the experiments which had begun 

 with the savage and had been brought to a 

 new meaning by Count Rumford. Joule set 

 himself to find out exactly how much heat is 

 equivalent to a given amount of work. He 

 applied sinking weights to the agitation of 

 water, and, taking elaborate precautions 

 against the escape of heat, he found that 

 1,390 pounds in descending one foot could 

 raise the temperature of a pound of water 

 by 1 C. Here at last was rendered an accu- 

 rate account of the enormous debt due to the 

 ability to kindle fire. ILES Flame, Elec- 

 tricity, and the Camera, ch. 7, p. 82. (D. & 

 McC., 1900.) 



2126. MEASUREMENT AMONG 

 NORTH-AMERICAN MOUND-BUILDERS 



Exactness of Lines, Angles, and Circles. 

 The squares or other rectangular works 

 never have a ditch, and the earth of which 

 they are composed appears to have been 

 taken up evenly from the surface, or from 

 large pits in the neighborhood. They vary 

 much in size; five or six of them, however, 

 are " exact squares, each side measuring one 

 thousand and eighty feet a coincidence 

 which could not possibly be accidental, and 

 which must possess some significance." The 

 circles also, in spite of their great size, are 

 so nearly round that the American archeol- 

 ogists consider themselves justified in con- 

 cluding that the mound-builders must have 

 had some standard of measurement, and 

 some means of determining angles. AVE- 

 BUBY Prehistoric Times, ch. 8, p. 246. (A., 

 1900.) 



2127. MEASUREMENT OF ENERGY 



The Foot-pound Exactness of Science. 

 This brings us to the discussion of what is 

 called the " mechanical equivalent " of heat. 

 It has been proven by experiment that the 

 quantity of heat necessary to raise one 

 pound of water to the temperature of one 

 degree F. is equal to that generated by a 

 pound weight falling from a height of 772 

 feet against the surface of the earth. Con- 

 versely, an amount of heat necessary to raise 

 a pound of water one degree F. in tempera- 

 ture would, if all is converted into mechan- 

 ical energy, be sufficient to raise a pound 

 weight 772 feet above the earth. The unit 

 of measurement called the " foot-pound " 

 has been adopted as a means of determining 

 the amount of energy expended in doing a 

 given piece of work. The foot-pound is a 

 unit of energy as expressed in work, and is 

 that amount of energy which is necessary to 

 raise one pound weight one foot high against 

 the force of gravity. It follows from this 

 that the amount of heat necessary to raise 

 a pound of water one degree F. is equal to 

 772 foot-pounds, which constitutes the me- 

 chanical equivalent of heat. We thus have 

 a means of measuring energy, whether me- 

 chanical or molecular. ELISHA GRAY Na- 

 ture's Miracles, vol. ii, ch. 1, p. 13. (F. H. 

 & H., 1900.) 



2128. MEASUREMENTS OF HEAT 

 OF SUN Coal Needed for Equal Supply. 

 The total amount of solar heat received by 

 the earth in a year, if distributed uniformly 

 over the earth's surface, would be sufficient 

 to liquefy a layer of ice 100 feet thick, cover- 

 ing the whole earth. The heat of the sun, if 

 used to melt a stratum of ice applied to the 

 sun's surface, would liquefy it at the rate of 

 2,400 feet an hour. It would boil per hour 

 700,000 millions of cubic miles of ice-cold 

 water. Expressed in another form, the heat 

 given out every hour by the sun is equal to 

 that which would be generated by the com- 

 bustion of a layer of coal, ten feet thick, 

 entirely surrounding the sun; hence the 

 heat emitted in a year is equal to that which 

 would be produced by the combustion of a 

 layer of coal seventeen miles in thickness. 

 TYNDALL Heat a Mode of Motion, lect. 17, p. 

 516. (A., 1900.) 



2129. MEASURES AMONG PRIMI- 

 TIVE MEN The Human Body the Universal 

 Standard. These ancient manufacturers 

 and builders had no government standards 

 of measuring their work, but referred every- 

 thing to their bodies. This system was far 

 more accurate among rude peoples, where 

 anthropometric differences between the 

 sexes and between individuals were very 

 slight. Many witnesses confirm the opinion 

 that every weapon or chungke-pole had its 

 proportion to the owner. Dr. Mathews says 

 that the Navajo pole for the great hoop 

 game was twice the span long, and Mr. Dor- 

 sey found that the Omaha arrow had to 

 measure from the inner angle of the elbow 

 to the tip of the middle finger, and thence 



