what he expects to discover, before he has finished his 

 labours. 



It would seem, however, that in spite of the precautions of tlie 

 older artists, their private ways of working, of producing substances, 

 of making colours, and effecting all kinds of material changes, 

 oozed out and became at last public property. But even after 

 their publication, these methods and receipts retained, paradoxi- 

 cally, the name of "Secrets,"* and many collections of them ap- 

 peared during the last three or four hundred years. It is beyond 

 my power to give a complete list of these ; my purpose at 

 present, as I have already said, is to exhibit a few of those to 

 Avhicli my attention happens to have been recently dii'ected, and 

 of which some at least ai'e possessed of a certain amount of archajo- 

 logical and bibliograjjhic interest. 



This set of books divides into several groups, but perfect classi- 

 fication of them is impossible on account of the way the themes 

 interweave. 



I. There are collections of secrets of nature, or treatises on 

 natural history, general science, and cosmogony. Of this set, 

 Pliny's history seems to have been the model. 



II. There are treatises on what was called natural magic (as 

 distinguished from black magic or necromancy) — that is, the pro- 

 duction of secret effects in optics, acoustics, magnetism, ttc, &c., 

 by natural causes. This is the form which natural philosoiihy 

 originally took. 



III. There are treatises which deal chiefly with chemical, phar- 

 maceutical, and medical secrets. 



IV. There are treatises on life and generation : physiological 

 secrets. 



V. There are ti-eatises on technical or art secrets, strictly so 

 called, and they may be arranged conveniently in two classes : 

 general collections containing receipts relating to a variety of arts, 

 and special collections containing receipts of use in one art cr 

 handicraft only. 



I have examples of each of these classes to exhibit. 

 The earliest medieval treatise on the subject of the practical arts 

 to which I can refer at the present nioment is that of Theophilus. 



* In the remarks which followed the reading of the jiaper it was pointed 

 out that not so long ago chemical works were known, everywhere in Scot- 

 land at least, as "secret works." Some are still practically such. 



