490 POPULAR LECTURES AM) ADDRESSES. 



promoted by laboratory work in a manner beyond 

 all conception. It is a kind of work in which also 

 patience and perseverance are promoted in a most 

 marked degree. No labour must be shrunk from ; 

 everything must be carefully done. There is this 

 which is satisfactory about it : that perseverance is 

 sure to be rewarded. There is no failure in physi- 

 cal science. We do not always find the particular 

 thing looked for ; we often find that what we 

 looked for does not exist, or that something else 

 exists very different from what we expected to 

 find : but that something is to be found in any 

 investigation entered upon with intelligence and 

 pursued with perseverance, is a certainty ; and also 

 that that something is not valueless follows as a 

 matter of course. Every additional knowledge of 

 the properties of matter is of value. 



A large part of the work of a physical or 

 chemical laboratory must be measurement. That 

 might seem rather trying work; "harsh and 

 crabbed " shall we say ? Who cares to measure 

 the length of a line in land-surveying, or of a piece 

 of cord, or of ribbon, or of cloth ? These may not 



