JOHN D ALT ON 507 



must be invoked. This achieved, we may assert that we have arrived 

 at that species of conceptual simplicity which we call a " law of nature." 

 On a broad view, it is fair to say that, prior to Dalton, investigation 

 and fancy pursued the one (i. e., the conception of "matter") through 

 the many (i. e., these three aspects of the problem). For, on the whole, 

 till we come to J. J. Becher (1635-82) and G. E. Stahl (1660-1734), 

 the element theory held the field. And this is only to affirm that men 

 were trying to master the properties of particular bodies, while reserving 

 the remoter question of the ultimate constitution of " matter." Eoger 

 Bacon's view, probably the least fantastic we possess, is exceedingly 

 significant of this. 



There are four Elements — fire, water, air, earth; that is, the properties of 

 their condition are four— heat, coldness, dryness and wetness; and hyle is the 

 thing in which there is nor heat, nor coldness, nor dryness, nor wetness, and a 

 body is not. And the Elements are made of hyle; and each of the elements is 

 transmuted into the nature of the other element and everything into everything 

 «lse. For barley is a horse by virtual possibility, that is, occult nature; and 

 wheat is a man by virtual possibility, and a man is wheat by virtual possibility. 



The age of phlogiston, with its theories of combustion, marks a 

 move to the second question. Men are now engaged in an effort to 

 relate phenomena. Or, as Stahl puts it, in his conspectus : Combustible 

 substance minus phlogiston is burnt substance — e. g., metals, sulphur, 

 phosphorus, etc., minus phlogiston, are metal calxes, sulphuric and 

 phosphoric acids, etc. On the other hand, burnt substance plus phlo- 

 giston is combustible substance — e. g., metal calxes, sulphuric and phos- 

 phoric acids, plus phlogiston supplied by carbon, are metals, sulphur, 

 phosphorus, etc. In a word, the most different phenomena, such as the 

 burning of carbon and the calcination of a metal, are shown to belong 

 to the same class, and to be explicable by a simple conceptual hypothesis. 

 Finally, when Lavoisier sent phlogiston by the board, the third question 

 came to the fore, and men began to ask, How can we weigh, measure 

 and enumerate the exact degree of relationship between the properties 

 of substances? Dalton ranks among the great epoch-makers, because 

 he first brought this inquiry within the range of practicable uniformity. 



Discussions about prior discovery, over which much time and no 

 little temper have been expended, prove profitless affairs, as a rule. You 

 see, error and loyalty are human. For instance, I am well aware that 

 scientific chemistry is dated usually from 1776, when Lavoisier made 

 the balance the chemical instrument: but you will bear with Sadler 16 

 and me if we travel a little farther back and, as loyal sons of alma 

 mater, find the initial point in the classical investigation of latent heat, 

 conducted by Black between 1759 and 1763, at Glasgow. Nevertheless, 

 as Dalton's priority has been impugned, we are bound to consider 

 the facts. 



16 Herbert C. Sadler, professor of naval architecture. 



