xxii INTRODUCTION. 



Natural Magnets. 



Permanent Artificial Magnets. 



Electro-Magnets. 



Methods of Magnetization. Effects of Magnetization. Conditions affecting 

 intensity of Magnetization": Temperature (chemical), composition, strains, &c. 



Magnetic Induction of all Substances. Diamagnetism. 



Measurement of intensity of magnetization, magnetic moment. 



Terrestrial Magnetism. Instruments for observation and automatic regis- 

 tration of the magnetic elements. 



ELECTRICITY. 



Instruments and apparatus employed in teaching, and in the investigations 

 and observations connected with : 



Production and Maintenance of Difference of Potential. Electrical 

 machines acting by friction, induction (doublers, replenishers, &c., Holz's and 

 Toppler's machines, &c.) ; galvanic batteries ; thermo-electric piles ; magneto- 

 electric machines. Other sources, such as pyro-electricity, pressure electricity, 

 cleavage, capillarity, osmose, &c. 



Detection and Measurement of Difference of Potential. Electroscopes, 

 electrometers, standards of electro-motive force, methods of comparison. 



Accumulation of Electricity. Insulators, condensers, accumulators, effects 

 due to accumulated electricity, distribution on conductors, polarisation of 

 dielectrics, &c. 



Measurement and Electric Quantity. Torsion balances, standard accumu- 

 lators, methods of comparing electric capacities and dielectric coefficients. 



Detection of Measurement of Electric Currents. Galvanoscopes, galvano- 

 meters, voltameters, electro-dynamometers, &c. 



Resistance. Standards of resistance, methods of comparing resistances, 

 methods of establishing absolute standards (British Association unit appar.). 



Effects of Electric Currents. Production of light, heat, electrolysis, electro- 

 diffusion. Action on magnets, soft iron (electro-magnets), action of currents 

 on currents. 



Technical Application of Electricity. Electric telegraph, &c. 



ASTRONOMY. 



Star maps, catalogues, globes, orreries, 



&c. 



Meridian instruments. 

 Arrangements for communicating true 



time, 

 Altazimuths, zenith-sectors, sextants, 



&c. 



T, , , , ( reflectors. 



Equatoreal telescopes < _ 



I refractors. 



Micrometers. 



Driving clocks. 



Special arrangements for 



Celestial photography. 



Spectroscopic observations. 



Thermo-electric observations. 

 Siderostats. 



