GLA SS-MAKING. 6 1 1 



GLASS-MAKING. 



V. GLASS IN SCIENCE. 



By C. HANFORD HENDERSON, 



PROFESSOR OF PHYSICS AND CHEMISTRY IN THE PHILADELPHIA MANUAL TRAINING SCHOOL. 



WHEN we compare the modern man, the product of many- 

 centuries of more or less continuous culture, with the men 

 of ancient Rome, and still more with the men of ancient Greece, 

 the impression unwillingly forces itself upon us that man has 

 somewhat deteriorated since the days of Carthage and Ther- 

 mopylae. The reflection is a discouraging one. But observe how 

 unavoidable it is. The modern man can not run so far or so fast, 

 can not see so well, hear so acutely, or speak so loud. All his 

 direct physical powers have suffered diminution. If the compari- 

 son be extended to the intellectual world, it is clearly manifest 

 that the loss of power in one direction has not been compensated 

 by the gain in another. One need have no great turn for Hellen- 

 ism to perceive that the average American, despite his boasting, 

 appears but a struggling child beside the heroes of either the 

 Olympian games or the Athenian groves. 



The effect of such a comparison as this is to make one question 

 the truth of human evolution, and to ask himself in all serious- 

 ness whether the history of the race is not one of retrogression 

 rather than of advance. But there is another way of looking at 

 the matter, and there are other factors which must needs be taken 

 into consideration. 



The suggestion, I believe, is due to Mr. Spencer that, in at- 

 tempting to measure man's physical power, the summary should 

 not be limited to his direct faculties, but should justly include 

 the acquisitions gained through the exercise of his intelligence. 

 Thus, while it is perfectly true that modern legs are not so sturdy 

 as Grecian legs, it must not be forgotten that by means of steamer 

 and railway the modern man can girdle the earth in a couple of 

 months, and can travel almost unlimited distances at the rate of 

 fifty miles an hour. At the present moment popular lecturers are 

 demonstrating that there is no reason why he should not go two 

 and a half miles a minute. Since this facility of movement is the 

 product of his own increasing development, we must admit that a 

 longer view establishes an increased power of locomotion in the 

 history of the race, and that even here evolution has been con- 

 stant. The modern vision is faulty and astigmatic. We are 

 veritable bats compared to the men of antiquity, or even to the 

 modern American Indian. But here, again, the brain has more 

 than compensated the defects of the eye. By means of the micro- 



