The Philosophy of Birds' Nests. 413 



The method, slightly modified, is also applicable — where 

 most processes fail — to the retention and restoration of ancient 

 ecclesiastical frescoes. In using the process, both for original 

 work and for restorations, I confess I prefer to adopt a somewhat 

 different plan for preparing the medium. I find the following 

 directions to yield an excellent product, and to be very easy to 

 carry out : — Dissolve three-quarters of an ounce of elemi in six 

 ounces of oil of spike, in a flask, by the aid of heat : the 

 fragments of bark in the elemi will sink to the bottom of the 

 vessel ; melt three ounces of white wax and one ounce of pure 

 white paraffine in another flask ; mix the two liquids together, 

 and allow the impurities to settle. Put twenty- two liquid 

 ounces of fine pale copal varnish — picture copal — in a tin can ; 

 keep the can plunged in boiling water for half an hour or 

 more; pour the elemi and wax mixture (also hot), into the 

 can, stir it, and keep warm some time longer. This pre- 

 paration may be used, diluted, etc., exactly as previously 

 directed. 



THE PHILOSOPHY OF BIRDS' NESTS. 



BY ALFRED R. WALLACE, F.Z.S., ETC. 



Birds, we are told, build their nests by instinct, while man con- 

 structs his dwelling by the exercise of reason. Birds never 

 change, but continue to build for ever on the self-same plan ; 

 man alters and improves his houses continually. Reason ad- 

 vances ; instinct is stationary. This doctrine is so very general 

 that it may almost be said to be universally adopted. Men 

 who agree on nothing else, accept this as a good explanation 

 of the facts. Philosophers and poets, metaphysicians and 

 divines, naturalists and the general public, not only agree in 

 believing this to be probable, but even adopt it as a sort of 

 axiom that is so self-evident as to need no proof, and use it as 

 the very foundation of their speculations on instinct and 

 reason. A belief so general, one would think, must rest on 

 indisputable facts, and be a logical deduction from them. Yet 

 I have come to the conclusion that not only is it very doubtful, 

 but absolutely erroneous; that it not only deviates widely 

 from the truth, but is in almost every particular exactly op- 

 posed to it. I believe, in short, that birds do not build their 

 nests by instiuct; that man does not construct his dwelling by 

 reason ; that birds do change and improve when affected by 

 the same causes that make men do so ; and that mankind 

 neither alter nor improve when they exist under conditions 

 similar to those which are almost universal among birds. 



