LABORATORY DIRECTIONS 51 



recognize his own failures and if possible to determine the 

 cause of the failure. And it is of even greater importance 

 to the student to be able to recognize and to show what re- 

 sults he should have obtained in an experiment which has 

 apparently failed. Not only the student, but especially 

 the instructor, should constantly be on the watch for atyp- 

 ical or unexpected results. Such chance observations have 

 often furnished the basis for valuable discoveries. 



Blue print copies of the best original tracings (chosen by 

 the instructor) should be made in the department, usually 

 by the technician, and should be furnished to the student at 

 a price which is just sufficient to cover the cost of the blue 

 print paper. (For directions for making blue prints, see 

 chapter on photography, page 510.) 



It is important that the permanent notes for each ex- 

 periment be written up as soon as possible after the ex- 

 periment is performed. The records or tracings should be 

 labeled in full and great care should be used to make them 

 as neat and accurate as possible. No more drum space 

 than is absolutely necessary should be used in making each 

 tracing. The drum paper should always be smoked good 

 and black. This is important for blue printing and for 

 publication if the instructor or anyone else should care to 

 have any tracing reproduced. It is also necessary for mak- 

 ing lantern slides. (See chapter on photography, page 

 500. ) 



Each group of students will be assigned to a table on 

 which to work. If a sufficient number of tables and the 

 floor space are available, it is advisable for each group to 

 have two tables, one for the experiment and the other to be 

 used as a side table for arranging apparatus, etc. When 

 frogs or turtles are used then the two sub-groups (of two 

 or three) may each have a table. If only one table is avail- 

 able, then for frog or turtle work the two sub-groups should 

 work one at each end of the table. It is preferable that the 

 drawers or lockers for the permanent apparatus be secured 



