XIV PREFACE. 



eighty degrees thermometer of Reamur. The lineal measure- 

 ment is the old French, in which the toise is equivalent to six 

 Parisian feet. The miles are geographical, fifteen to a 

 degree of the equator. The longitudes are calculated from 

 the first meridian of the Parisian Observatory. 



Berlin, March, 1849. 



