VI ELEMENTS OF LABOKATORY WORK 



severe. It may be noticed that while tables are added to show 

 the results of accurate observers, and to give information as 

 to relative magnitudes, the numerical values resulting from the 

 selected experiments have been generally left to be worked out 

 by the students themselves from their own observations. The 

 word speed has been used to denote the rate of motion of a 

 particle along its path, in preference to the term velocity, 

 which is now generally reserved to designate a quantity having 

 both magnitude and direction, i.e. a vector. The sections 

 numbered 3, 7, 12, 13, 14, 15, 24, 25, and 26, together with 

 many of the additional exercises, may be omitted by be- 

 ginners. 



Rooms devoted to practical science, and well equipped, are 

 nowadays considered a necessary part of all public schools and 

 colleges, and this book is simply intended to be used as a hand- 

 book in such laboratories. An effort has been made to arrange 

 a practical and progressive course which shall touch upon the 

 chief problems, and point out the main lines of investigation 

 in Natural Science, in preference to an attempt at explaining 

 any one branch in detail. It is also hoped that the course 

 may give some training in that habit of directly appealing to 

 nature, rather than to theories, which is the root of all scientific 

 progress, although unfortunately it is not always made the 

 basis of scientific education, partly from want of time and 

 partly from want of appliances. 



A. G. EARL. 



TONBBIDQE: 1890. 



