16 THE REV. W. WHEWELL ON THE EMPIRICAL LAWS 



of the collections which the subject will require, to place it on a par with the other 

 provinces of physical astronomy. The laws which connect the course of the observed 

 tides with the motions and distances of the sun and moon are not known for any 

 single port ; and the tables, which in every other province of physics are the result 

 of the knowledge which our men of science have accumulated for us, are, in this 

 department, published by persons possessing and professing no theoretical views on 

 the subject ; and the metliods by which they are calculated are not only not a portion 

 of our published knowledge, but are guarded as secrets, and handed down as private 

 property from one generation to another*. 



Of course it cannot be intended here to speak with any disrespect of the persons 

 who have calculated tide tables under these circumstances. Their labours are useful 

 to the community in proportion as their tables are exact, which some of them are to 

 a very remarkable degree. And, as no one thinks of condemning other persons who 

 make a profit of any peculiar and secret knowledge which they may possess con- 

 nected with any of the useful arts, there would be no justice in blaming those who 

 do the same with respect to secrets which concern one of the most important arts, 

 namely, navigation. But the circumstance most worthy of remark is, that there 

 should he secrets in such a matter ; that on such a subject our men of science should 

 be ignorant of, and unable to discover, that which persons of much less elevated pre- 

 tensions know and apply ; that the laws which are to be collected either by the 

 observation of facts, or by the deductions of theory, should not be known to our phi- 

 losophers by either method, and yet should be in the possession of other persons, to 

 a considerable extent. This circumstance makes our knowledge of the tides assume 

 the character rather of a mere practical art, than of a portion of that complete and 

 perfect science of which the other consequences of the law of universal gravitation 

 supply examples. ■ 



Some persons may conceive that, in what has been said, I am disparaging too much 

 the labours of the great mathematicians, Newton, Bernoulli, Laplace and others, 

 who have employed their skill on this subject. But this opinion cannot, I conceive, 

 be maintained with justice. It is well known that all the mathematical solutions of 

 the problem have confessedly gone upon suppositions very remote from the real facts : 

 Newton and Bernoulli, for instance, have assumed the form of the fluid spheroid, 

 under the influence of the sun and moon, to be the form of equilibrium : Laplace has 

 supposed the whole globe to be covered with water of an uniform depth. It is in no 

 degree clear, that investigations conducted on such assumptions will give us even an 

 approximation to the true result ; and the only way in which the assumptions could 

 be justified, would be by our finding, from observation, that the laws of the facts are 

 such, or nearly such, as these hypothetical calculations give. If this agreement were 



* What is here asserted was strictly true till the publication of Mr. Lubbock's Memoir on the Tides of the 

 Port of London, and his Tide Tables, founded on his discussion of these. At present his Tide Tables are calcu- 

 lated by published methods ; but the laws which these methods imply have not yet been compared with theory. 



