SCIENTIFIC DRAWING AND DESCRIPTION 



original object is very important, and should always be 

 expressed. This is usually done in good monographs 

 by a fraction ; if the drawing is one-half the size of 

 the original, the fraction ^ should be placed beside the 

 drawing ; if the drawing is twice the size of the origi- 

 nal object, it is expressed by ^ ; if the same size, by ^, 

 and so forth. The best general rule as to scale is to 

 make the drawing as small as will allow all features 

 intended to be represented to be clearly seen. If, 

 however, making clear certain of the smallest features 

 would make the entire outline very large, it is better 

 to make two drawings, one showing the details only 

 upon a larger scale. It is well to give the students 

 small pasteboard rulers, preferably on the metric sys- 

 tem, which can be kept in pockets in the back of 

 the laboratory books, and used for making the scale 

 of the drawings correct. 



The different features of the drawings should be 

 carefully labelled to show their names. The exact 

 spots to which the names apply should be shown by 

 fine ruled dotted lines, as in Figs. 12, 13, 14. In 

 books, for appearance' sake, usually only letters are 

 thus attached to the drawings, and the corresponding 

 names are given in an explanation below or in the 

 text. But in laboratory work I have found that the 

 extra neatness of this plan does not compensate for 

 the loss of time required of the teacher to look 

 up the explanations, and I think it much better to 



