160 THE THEORY OF GRAVITATION. 



precision and more as the phenomena themselves furnish, for these 

 laws are the inevitable consequences of the constitutions I have 

 supposed. 



Second. Although I here present these constitutions crudely and 

 without proof, as if they were gratuitous hypotheses and adventurous 

 fictions, the fair-minded reader will perfectly comprehend that I have 

 at hand some presumptions, at least, in their favor (independent of the 

 perfect accord with all the phenomena), but which I withhold as too 

 extended for development in this place. These suppositions may then 

 be regarded as theorems published without demonstration. 



Third. Their number is likely to inspire some opposition at first 

 glance; but the attentive mind will not fail to see that they are but 

 details into which I have wished to enter because of the novelty of 

 this doctrine, and that they will be readily understood when it shall 

 have become sufficiently well known that its students may attend under 

 favorable circumstances to the details. If the authors who have writ- 

 ten upon hydrodynamics, aeronautics, or optics had had readers who 

 doubted the existence of water, air, and light, and who consequently 

 indulged no tacit supposition upon equalities or compensations of 

 which no express mention was made, they, too, would be obliged to add 

 a great number of explanations to their definitions which instructed 

 or indulgent readers might well dispense with. We do not accept of 

 hints, and sano sensu, except for propositions which are familiar and in 

 whose favor there is a predisposition. 



