EXPLANATIONS. 



Polarization.— Most essential oils, and the solutions of several 

 substanees described in this book are capable of effecting the deviation 



rftY 



The amount of this rotatory power cannot 

 be regarded as constant in essential oils, and is greatly influenced by 

 various causes. As to alkaloids and other 



quently depend 



organic compounds, the 



and quantity of the solvent. The authors 



thou 



INCHES CENTIMETRES 



to 



cases the results of such optical investigations, 



determin 

 invented 



Wild 



described in Poggen- 



Chemnie 



(1864) 



2 



imjyei 



de St. Petersbourg, tome viii. (1869) p. 33. 



Measurements and Weights.-The authors 

 regret to have been unable to adopt one standard 

 system of stating measurements. They have 

 mostly employed the English inch: the accom- 

 panying woodcut will facilitate its comparison 

 with the French decimal scale. The word 

 metre is indicated in the text by the contraction 

 mm.; micromillimetre ,s'igmfymg the thousandth 

 part of a millimetre, and only used in reference 

 to the microscope, is abbreviated thus, mkm. 



B 



m 

 o 



X 

 X 



n 



2 

 -4 



X 



w 



rnilli 



m 



t/i 

 o 



X 



3 



1 inch 

 1 gallon 



millimetres 



m 



1 



# 



ounce (oz.) avdp. 

 1 lb. avoirdupois = 4<53'o9 



4'543 litres. 

 28-34 grammes 



X 



-I 



m 



- 



H 



(0 



4 



t_ 



j> 



I cwt. 



1 ton 



1 kilogramme 

 1 pecul 



lb 



2240 



50*8 kilogrammes 



}> 



1016 



f) 



2-204 lb. avoirdupois. 



U7 



UJ 



bJ 



S 



183-33 lb. 



60*471) kilogrammes, 



1 



s 



4 



6 







7 



8 



9 



Thermometer.— The Centigrade Thermometer has been alone 

 adopted. The following table is given for companng the degrees of 



the Centigrade "or Celsius Thermometer with those of Fahrenheit's 

 Seale. 



