58 SEC. 3. MEASUREMENT. 



taking off the apparatus from the barrel of the cannon, between the two 

 arms, so that the contact lever again indicates zero. The same scale serves 

 also for measuring the interior diameter of the rings. The apparatus has 

 been constructed and made by G. Brauer at St. Petersburg. 



267a. Photograph of an Apparatus for measuring the 



eccentricity of the chamber and the curve of the bore of cannons. 



G. Brauer, St. Petersburg. 



The apparatus consists of two parts : 



1 . A body, wHich is pressed into the mouth of the cannon by means of 

 an endless screw. In this screw a telescope is fixed which can be turned 

 about its own axis, and is provided with a filar micrometer and a position 

 circle. 



2. A piece, which can be slided along the barrel, being turnable about the 

 axis of the bore, and in whose centre is a glass plate with engraved cross. 

 This cross is viewed through the telescope before mentioned, and the deter- 

 mination of the position of the cross on the filar micrometer indicates the 

 elements for determining the curve of the bore and the eccentricity of the 

 chamber. 



The apparatus was constructed by the exhibitor for the Russian Marine 

 Artillery Department. 



267b. Instrument for Measuring the Bore of Cannons 



(Etoile Mobile). G. Brauer, St. Petersburg. 



This instrument consists of a ring, in which two parallel rods slide longi- 

 tudinally side by side, and one of which carries the scale, the other its 

 vernier. The sliding rods are pressed asunder by means of springs, so that 

 their exterior steel ends touch the side of the bore to be measured. As this 

 contact must not take place during adjustment, the sliding rods are brought 

 together by a bolt. A screw perpendicularly under the sliding rods is in- 

 tended for adjusting them according to the greatest diameter, which has to 

 be done afresh at each measurement. If the chamber of a breech-loading gun 

 is to be measured with the apparatus a set of two rings has to be added, of 

 which the one in front carries a telescope for viewing the scale. The two 

 exterior rings are joined to each other by four bars, and these bars have a 

 movement in the centre ring, which during the operation of measuring L 

 pressed into the back part of the cannon bore by means of four screws, and 

 the whole apparatus is then moved as required. 



267c. Apparatus constructed for measuring the exterior 

 diameter of small cylinders with an accuracy of 0' 001 inch. 



G. Brauer, St. Petersburg. 



This apparatus, which was employed in the experiments on the elasticity 

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

 pillar and a contact-lever, which can be adjusted 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. 



267a. Apparatus for Measuring the Breeches of 

 Large Guns. M. Gadolin, St. Petersburg. 



