MEMORANDA 



275 



Weight. 



1 gramme 

 1 oz. 

 1 grain 



15-432 grains 

 = 28-35 grammes 

 = -0648 gramme 



USEFUL MEMORANDA 



1 mm. 

 2^ inch 



^siio o i 

 5 cm. 



3mm. 

 2-5 mm. 



2 mm. 



5 /* 



YJu- inch 

 4 litres 



=Jg inch 



=100 micra 

 = 1 micron 

 =2 inches 

 = Jinch 

 =-J^ inch 

 == T- inch 



= 5-oV o incn 

 =-25 mm. 



= 7 pints 

 2 grammes =31 grains 



To convert grains per oz. to grammes per litre, multiply 

 grains by 2-3. 



To convert grammes per litre to grains per oz., multiply 

 grammes by 0-44. 



To convert c.c's. per litre to minims per oz., divide the 

 c.c's. by 2. 



Enlargement Table 



The distance between lens and object for any enlargement 

 is obtained by dividing the camera extension, as given in the 

 table, by the enlargement. 



POLISH FOR FERROTYPE PLATES 



Spermaceti wax 20 grains 



Benzole . . 1 oz. 



or 



45 grammes 

 1000 c.c. 



