- OBSERVATION AND DESCRIPTION. 453 



shadow thrown upon the moon is circular ; or this, that on the sea, or any- 

 extensive plain, our horizon is always a circle ; either of which marks is in- 

 compatible with any other than a globular form. I assert further, that the 

 earth is that particular kind of a globe which is termed an oblate spheroid ; 

 because it is found by measurement in the direction of the meridian, that 

 the length on the surface of the earth which subtends a given angle at its 

 centre, diminishes as we recede from the equator and approach the poles. 

 But these propositions, that the earth is globular, and that it is an oblate 

 spheroid, assert, each of them, an individual fact ; in its own nature capa- 

 ble of being perceived by the senses when the requisite organs and the nec- 

 essary position are supposed, and only not actually perceived because those 

 organs and that position are wanting. This identification of the earth, 

 first as a globe, and next as an oblate spheroid, which, if the fact could have 

 been seen, would have been called a description of the figure of the earth, 

 may without impropriety be so called when, instead of being seen, it is in- 

 ferred. But we could not without impropriety call either of these asser- 

 tions an induction from facts respecting the earth. They are not general 

 propositions collected from particular facts, but particular facts deduced 

 from general propositions. They are conclusions obtained deductively, 

 from premises originating in induction : but of these premises some were 

 not obtained by observation of the earth, nor had any peculiar reference 

 to it. 



If, then, the truth respecting the figure of the earth is not an induction, 

 why should the truth respecting the figure of the earth's orbit be so ? The 

 two cases only differ in this, that the form of the orbit was not, like the 

 form of the earth itself, deduced by ratiocination from facts which were 

 marks of ellipticity, but was got at by boldly guessing that the path was 

 an ellipse, and finding afterward, on examination, that the observations were 

 in harmony with the hypothesis. According to Dr. Whewell, however, this 

 process of guessing and verifying our guesses is not only induction, but the 

 whole of induction : no other exposition can be given of that logical opera- 

 tion. That he is wrong in the latter assertion, the whole of the preceding 

 book has, I hope, sufficiently proved ; and that the process by which the 

 ellipticity of the planetary orbits was ascertained, is not induction at all, 

 was attempted to be shown in the second chapter of the same Book.* We 

 are now, however, prepared to go more into the heart of the matter than at 

 that earlier period of our inquiry, and to show, not merely what the opera- 

 tion in question is not, but what it is. 



§ 4. We observed, in the second chapter, that the proposition " the earth 

 moves in an ellipse," so far as it only serves for the colligation or connect- 

 ing together of actual observations (that is, as it only affirms that the ob- 

 served positions of the earth may be correctly represented by as many 

 points in the circumference of an imaginary ellipse), is not an induction, 

 but a description : it is an induction, only when it affirms that the interme- 

 diate positions, of which there has been no direct observation, would be 

 found to correspond to the remaining points of th^ same elliptic circumfer- 

 ence. Now, though this real induction is one thing, and the description 

 another, we are in a very different condition for making the induction be- 

 fore we have obtained the description, and after it. For inasmuch as the 

 description, like all other descriptions, contains the assertion of a resem- 



* Sapra, book iii., chap, ii., § 3, 4, 5. 



