ADVANCEMENT OF LEARNING 219 



is tried in another of the like kind; thus the making of 

 paper is hitherto confined to linen, and not applied to silk, 

 unless among the Chinese, 13 nor to hair-stuffs and camblets, 

 nor to cotton and skins; though these three seem to be more 

 unfit for the purpose, and so should be tried in mixture 

 rather than separate. Again, engrafting is practiced in fruit 

 trees, but rarely in wild ones; yet an elm grafted upon an 

 elm is said to produce great foliage for shade. Incision 

 likewise in flowers is very rare, though now the experi 

 ment begins to be made upon musk-roses, which are suc 

 cessfully inoculated upon common ones. We also place the 

 variations on the side of the thing among the variations in 

 the matter. Thus we see a scion grafted upon the trunk of 

 a tree thrives better than if set in earth; and why should 

 not onion-seed set in a green onion grow better than when 

 sown in the ground by itself, a root being here substituted 

 for the trunk, so as to make a kind of incision in the root? 



An experiment may be varied in the efficient. Thus, 

 as the sun s rays are so contracted by a burning glass, and 

 heightened to such a degree as to fire any combustible 

 matter, may not the rays of the moon, by the same means, 

 be actuated to some small degree of warmth, so as to show 

 whether all the heavenly bodies are potentially hot? and 

 as luminous heats are thus increased by glasses, may not 

 opaque heats, as of stones and metals, before ignition, be 

 increased likewise, or is there not some proportion of light 

 here also? Amber and jet, chafed, attract straws, whence 

 query, if they will not do the same when warmed at the 

 fire? 



An experiment may be varied in quantity, wherein very 

 great care is required, as being subject to various errors. 

 For men imagine, that upon increasing the quantity the 

 virtue should increase proportionably ; and this they com 

 monly postulate as a mathematical certainty, and yet it is 

 utterly false. Suppose a leaden ball of a pound weight, let 



12 The Chinese also manufacture their paper out of the interior bark of 

 cae. Ed. 



