20 N'IXF,TEENTH REPORT. 



their time, and in many otli(.r conditions. To an even greater degree 

 the overturning of scientiHc doctrines has been due to the failure of both 

 the scientists and their critics to distinguish clearly between legitimate 

 theory within those fields where views may be rigidly tested, and 

 audacious conjectures M-hich have been ottered under the verisimilitude 

 of facts to explain problems whose complete solution belongs to the 

 remote future, if they may not be regarded as insoluble by any' methods 

 which have yet been discovered. 



The ]>rocess of eruption within a volcanic vent as regards its physical 

 and chemical aspects oilers a problem wliich, though by no means simple, 

 may yet be subjected to observation and experimentation and doubtless 

 belongs to the realm of soluble scientific ])roblems. The materials 

 present at the earth's center and their peculiar state of aggregation, are 

 by contrast very largely a subject of conjecture, and attempts to class 

 these problems together lead to inexcusable confusion. 



A theory has been defined as an explanation founded upon inferences 

 drawn from principles which are established by evidence. By contrast the 

 hypothesis is a supposition as yet untested. The working hypothesis of 

 the scientist occupies an intermediate position and aims to explain, at 

 least in part and better than any other, a set of related phenomena 

 which are already known, and it is considered to be in a probationary 

 stage until confirmed through rigid tests the nature of which is suggested 

 by the hypothesis itself. When so examined it may be found wanting; 

 but, if well founded, experimentation is likely to result in its improve- 

 ment by pruning of error quite as much as through enlargement of the 

 body of truth which it contains. 



The inheritance of knowledge by the ancients was, compared to ours, 

 small indeed ; and with their limited resources in materials and in 

 methods of investigation, even more than we, they saw "through a glass 

 darkly. " It was therefore but natural that the theories which they 

 evolved should have been largely the product of introspective reasoning. 

 In consequence it was in the field of mathematics that they achieved their 

 greatest triumphs, and as an inheritance a mathematical language was 

 common to other fields of science even late in the seventeenth century. 

 Viewing the marvels of the universe with their limited outfit of exact 

 knowledge, the ancient philosophers invoked the supernatural and the 

 mysterious to explain whatever was baffling and otherwise incompre- 

 hensible. Without books the dissemination of knowledge was limited to 

 the narrowest channels and was accomplished bj- the disciples of each 

 leader of thought, who was thus under the temptation of finding an 

 answer to all questions and founding an individual school of philosophy. 



With the invasions of the barbarian Huns and the Germanic tribes in 

 the fifth century of the Christian era, there ensued the eclipse of civiliza- 



