vi PREFACE. 



he treats, and on the labours of previous writers. In the 

 former category my special thanks are due to Professors 

 EEINOLD and SILVANUS THOMPSON, for valuable assistance 

 in the section on Electricity ; to WILLIAM ELLIS, Esq., for 

 some Tables in Terrestrial Magnetism ; and to H. J. CHANEY, 

 Esq., for much help in the difficult subject of the English and 

 Metric Measures. I am also most grateful to my friend and 

 former colleague, DONALD MACALISTER, Esq., who has kindly 

 read both the MS. and the proof, numerous corrections and 

 suggestions in which are due to his accurate knowledge and 

 sound judgment. 



The following list of authorities, to whom I am more 

 particularly indebted, will serve both as an acknowledgment 

 of my obligation, and as a guide to those who desire further 

 information than could be compressed into the limited space 

 at my disposal. 



S. L. 



HARROW, 



March 1884. 



LIST OF CHIEF AUTHORITIES. 



Agenda du Chiiniste. Paris. 1882. 



Annuaire, public par le Bureau des Longitudes. Paris. 1883. 



Barlow. Tables of Squares, Cubes, Square Roots, Cube Roots, 

 Reciprocals. London. 1875. 



R. Biedermann. Chemiker Kalender. Berlin, 1884. 



F. W. Clarke. Constants of Nature, I. and Suppl., Specific 

 Gravities, Boiling and Melting points. II., Specific Heats. III., 

 Expansion by Heat. Washington. 1873. 



