BOOK IL] APIIORISM& 157 



But natural aiid experimental history is so varied and diffuse, 

 that it confounds and distracts the understanding unless it be 

 fixed and exhibited in due order. We must, therefore, ierm 

 tables and co-ordinations of instances, upon such a plan, and in 

 such order, that the understanding may be enabled to act upon 

 them. 



Even when this is done, the understandin<r, left to itself and 

 to its own operation, is incompetent and untit to construct its 

 axioms without direction and support. Our third ministration, 

 therefore, must be true and letritii fintf jn^"'^*^''^" *'" ""^7 ^'^y ^ 

 interpretation. TVe must begin, iiowever, at the end, and go 

 b^ai^k ujiaiu tTJ the others. 



XL The invcstifi^ation of forms proceeds thus : a nature beinj^ 

 piven, we must first present to the understandincr all the known 

 instances which a«;rec in the same nature, although the subject 

 matter be considerably diversified. And this collection must bo 

 made as a more history, and without any premature reflection, or 

 too great degree of refinement. For instance ; take the investi- 

 gation of the form of heat. 



Instances agreeing in the Form of Heat. 



1. The rays of the sun, particularly in summer, and at noon. 



2. The same reflected and condensed, as between mountains, 

 or along walls, and particularly in burning mirrors. 



3. Ignited meteors. 



4. Burning lightning. 



5. Eruptions of flames from the cavities of mountains, &c. 



6. Flame of every kind. 



7. Ignited solids. 



8. Natural warm baths. 



9. Wiirm or heated licpiids. 



10. Warm vapours and smoke ; and the air itself, which 

 admits a most powerful and violent heat if confined, as in rever- 

 berating furnaces. 



11. Damp hot weather, arising from the constitution of the 

 air, without any reference to the time of the year. 



12. Confined and subterraneous air in some caverns, parti- 

 cularly in winter. 



13. All shaggy substances, as wool, the skins of animals, anl 

 (ho plumage of birds, contain some heat. 



14 All bodies, both solid and liquid, dense and rare (as the 

 air itself), placed near fire for any time. 



15. Sparks arising from the violent percussion of flint and 

 steel. 



IG. All bodies rubbed violently, as stone, wood, cloth, &c., sc 

 that rudders, and axles of wheels, sometimes catch fire, and the 

 West Indians obtain fire by attrition. 



17 Orceu and moist vegetable matter confined and rubbed 



