730 RKPORT OF NATIONAL MUSEUM, 1S91. 



913. INSTRUJVIENT.S OF PRECISION FOR THE TE.ST OF FORCE, 8pEED, ETC. 



Weight and specific gravity : Standards of weights and their coiui»ari.sou — 

 Scales, balances, steelyards, assay balances, and ordinary scales for heavy 

 weights special finding. — Instruments to determine specific gravity and 

 density— Hyilroineters, aerometers, invariable pendulums, etc. 



Speed: Tacliyineters. Current meters, shi))s' logs, electrical logs. 



Force: Dynamometers, (iaiiges for liydraulic, pneumatic and steam ma- 

 chinery. 



Heat and otlier physical effects: Tli irmometcrs and other instruments to 

 measure meteorological efi'ects. iiaronieters., pyrometers, eudiometers, 

 electrometers, rlieometers, magnetometers, etc. (See also Meteorology, 

 Class 926.) 



Tone: Tuning forks and pipes. 



Electrical apparatus: Friction machines. Condensers and miscellaneous 

 api)aratus to illustrate the discharge. Galvanic batteries and accessories 

 to illustrate dynamical electricity. Electro-magnetic apparatus, induc- 

 tion machines, Ruhmkorft' coils, eti^ Magnets and magneto-electric appa- 

 ratus. 



914. Instruments of Precision. 



Number, time, etc. 



Number. 



Tallies, automatic registers and al>aci. Mathematical instruments. Calcu- 

 lating machines. 



Time. (Horology.) 



Ancieut chronometry. Planetary motion. Dials, hour-glasses. 



MocUiru chrouometry — Clepsydra, clocks, weight, spring and balance, electric 

 and astronomical. Watches, chronometers, stop watches. 



Almanacs, calendars and time-tables. Ephemerides. 



Registration of musical time or length. Metronomes. 



915. iNSTRUiMENTS ACCESSORY TO RESEARCH. 



Comparative meteorology: Scales of ^'eights and measures of different 

 countries. 



Instruments accessory to research : Microscopes and lenses and their acces- 

 sories. Telescopes and lenses and their accessories. Apparatus for polar- 

 ization, refraction, photometry, etc. Spectacles and eye-glasses, field and 

 opera-glasses, graphoscopes and stereoscopes. Instruments for the investi- 

 gation of the principal mediums of heat, light, electricity, etc. Spectro- 

 scopes and accessories for spectrum analysis. Polariscopes. Thermotic 

 apparatus. 



Instruments used in anatomical and physiological investigation. 



Instruments used in chemical and assay work. 



Tables of all kinds for use in computation. 



916. Meteorology. 



Mod<nn meteorology and weather forecasts. History and present methods. 

 Meteorological instruuients. (See also Class 922.) 



Harometers, hygrometers and rain gauges. Maps, bulletins. Blanks for 

 reports. Methods of recording, reducing and ri'porting observations. 



917. Applied Science. 



Mechanical engineering. 

 Civil engineering. 

 Navigation. 

 Iiiventi(m. 



All other departments of applied sciences, literature, statistics, and full ex- 

 hibition of methiids and instruments not elsewhere shown. 



