226 THE POPULAR SCIENCE MONTHLY. 



the most natural and the best. If any one will put his faith in recipes, 

 I would remind him of the history of the sale of indulgences. We 

 look back with indignation to Tetzel's scandalous work, but how many 

 people still think they can purchase health by gorging themselves 

 with medicines ! Consumptives form no small portion of this class. 

 The treatment here recommended costs no money, but demands only 

 will, self-conquest, and perseverance. The treatment is not so com- 

 plicated as it may appear ; it is simply a movement and an air cure, 

 or, more briefly, an "attempering" cure, for effeminacy is the source 

 of all colds, coughs, and consumption, and hardening is the only pro- 

 tection and remedy against them. Der gemeinnutzige Gesimdheits- 

 Almanach. 



^Q++~ 



THE TIDES. 



By Pkofessor ELIAS SCHNEIDER. 



II. 



APART of the theory of the tides presented in our text-books 

 has been pronounced absurd in my first article. It is also a 

 matter of amazement that the effect of centrifugal force is entirely 

 ignored in these text-books. That the propelling force arising from 

 this cause should be utterly disregarded in an explanation of the tides 

 is very remarkable. And yet the existence of such a force is so easily 

 demonstrated that nothing else seems necessary to prove it to be one 

 of the causes of the tides, than what was presented in my first article. 

 I will, however, give additional force to my reasoning by citing the 

 results of actual experiment. 



It may be shown that there is an actual difference in the amount 

 of centrifugal force felt at any part of the earth's surface during 

 different times of the twenty-four hours of one axial rotation ; and 

 also at different times of the earth's revolution around her centre of 

 motion. Theory implies that when any portion of the earth's sur- 

 face is moving toward that point in her orbit where such surface 

 makes the most rapid sweep around the centre of motion, the greatest 

 amount of centrifugal force must be felt at such surface ; and that, 

 when this part moves toward that point of the earth's orbit where it 

 makes the slowest sweep around the centre of motion, the least amount 

 of centrifugal force must be felt. Now, it is very evident that any 

 portion of the earth's surface which is most remote from the centre of 

 her motion, whether that centre be the sun or the centre of gravity 

 between herself and the moon, makes the most rapid sweep, and that 

 consequently her waters must feel the greatest amount of centrifugal 

 force at that time. 



