4M 



how many divisions (e.g., two) any body (e.g. a blood 

 cell) covers, and multiply by ' the value ' of each 

 eyepiece scale for this combination of lenses. This 

 method is more accurate than the following. 



Method II. It is necessary to have a camera lucida 

 (the upright pattern is most convenient). Adjust 

 the light of the mirror and the diaphragms of the 

 camera lucida so that the object and the tip of the 

 drawing pencil are both clearly seen. Mark out the 

 required dimensions of the object, e.g., length and 

 breadth, on the paper placed at the right-hand side 

 of the microscope, using the right eye for observing. 

 Now place a millimetre scale divided into hundredths 

 on the stage instead of the object. Draw the scale 

 on the paper just below the object. Read off 

 directly the size of the object in millimetres. The 

 smallest amount that can be measured is TUO mm. = 



NOTE. By measuring the magnified size as drawn and dividing 

 this by the actual known size of the stage micrometer the magnifi- 

 cation of the microscope is given. 



WEIGHTS AND MEASURES, ETC. 



1. Conversion from one Temperature Scale to 

 another. 



C = F- 32 



5 " 9 

 Thus to convert 100 F. to centigrade 



100 - 32 C 



~Y 5 



2. Formula for Dilution of Solutions. The number 

 of parts required to dilute from one part of a solution 

 of strength x per cent, to another strength y per cent. 



, x 



is- i. 



y 



