94 Mr Whewell's Address to the British Association 



since those which Pound took at the request of Newton. Yet 

 on this case, if an accuracy and certainty worthy of the present 

 condition of Astronomy were to be aimed at, the requisite ob- 

 servations could not be few nor the calculation easy, when it is 

 considered in how complex a manner the satellites disturb each 

 other's motions. But the Meeting will learn with pleasure that 

 the task which he thus pointed out to others, he has himself in 

 the intervening time executed in the most complete manner. 

 He has weighed the mass of Jupiter in the way he thus recom. 

 mended ; and it may shew the wonderful perfection of such as. 

 tronomical measures to state, that he has proved with certainty, 

 that this mass is more than 322 and less than 323 times the mass 

 of the terrestrial globe on which we stand. 



Such is Astronomy ; but in proceeding to other sciences, our 

 condition and our task are of a far different kind. Instead of 

 developing our theories, we have to establish them ; instead of 

 determining our data and rules with the last accuracy, we have 

 to obtain first approximations to them. This indeed, may be 

 asserted of the iiext subject on the list, though that is, in its 

 principles, a branch of Physical Astronomy ; for that alone of 

 all the branches of Physical Astronomy had been almost or al- 

 together neglected by men of science. I speak of the science of 

 the Tides. Mr Lubbock terminated his Report on this sub- 

 ject, by lamenting in Laplace's- words this unmerited neglect. 

 He himself in England, and Laplace in Prance^ were indeed 

 the only mathematicians who had applied themselves to do some 

 portion of what was to be done with respect to this subject. 

 Since our Meeting last year, Mr Dessiou has, under Mr Lub- 

 bock's direction, compared the tides of London, Sheerness, 

 Portsmouth, Plymouth, Brest, and St Helena ; and the compa- 

 rison has brought to light very remarkable agreements in the law 

 which regulates the time of high water, agreements both with 

 each other and with theory ; and has at the same time brought 

 into view some anomalies which will give a strong impulse to 

 the curiosity with which we shall examine the records of future 

 observations at some of these places and at many others. I may 

 perhaps here take the liberty of mentioning my own attempts 

 since our last Meeting, to contribute something bearing on this 

 departmerrt. It appeared to me that our knowledge of one par- 



