50 SEC. 3. MEASUREMENT. 



267c. Apparatus constructed for measuring the exterior 

 diameter of small cylinders with an accuracy of 0*001 inches. 



G. Brauer, St. Petersburg. 



This apparatus, which was employed at the experiments as to the elasticity 

 of gun-metals, steel, cast-iron, &c.,in Russia, is provided with an unmoveable 

 pillar and a contact-lever, which can be displaced by means of a screw-move- 

 ment. The cylinder to be measured is placed between the two, and the screw 

 turned until the lever points to zero, and then the reading is effected by the 

 vernier of the longitudinal scale. 



267 d, Apparatus for Measuring the Length of the 

 Impressions made by the Rodman Scale. 



Technological Institute at St. Petersburg. 



The copper plate, on which is the impression to be measured, is placed on 

 the sledge of the apparatus, and then one end of the impression after the other 

 brought under the thread cross of the microscope by means of the screw of 

 the sledge, whereupon the reading can be made at the top of the screw. By 

 means of an ocular micrometer also shorter longitudinal dimensions can be 

 measured. 



The apparatus belongs to the Technological Institute at St. Petersburg. 



271. Calliper, with Dial, of the inch English measure, 

 divided into eighths of an inch. M. Isvardjfils. 



272. Calliper, with Dial of two centimetres, divided into 

 tenths of a millimetre. M. Isvardfils. 



283. Cylindrical Gauges differing in diameter by one .ten 

 thousandth of an inch. Other gauges and specimens of surfaces. 



Royal School of Mines. 



284. Universal Calliper, with .slide and reverse action. 

 Geneva Association for Constructing Scientific Instru- 

 ments. 



Instrument of measurement, for ascertaining equally the thickness, the 

 inner diameter of tubes, and their height. The latter by reversing the 

 moveable nozzle. 



286. Apparatus for measuring accurately the Diameter 

 of Wires, for testing whether pivots and other turned objects are 

 perfectly circular in form, and for the determination of the error 

 when they are not truly circular. 



Landsberg and Wolpers, Hanover. 



287. Apparatus for measuring the Thickness of thin 

 metal plates, sheets of paper, &c. 



Landsberg and Wolpers, Hanover. 



288. Calliper-Compasses for larger arcs. 



Landsberg and Wolpers, Hanover. 



288a. Photographs, showing two kinds of machines for 

 measuring with great precision the alterations in shape produced 

 in metals by tension and compression. Dumoulin Froment, Paris. 



