134 



SCIENTIFIC NEAVS. 



[Aug. ist, iS 



When the bathymeter is lowered in the water there is a 

 greater pressure on the outside of the tube d than within, 

 consequently it is somewhat compressed, and the extent of 

 its compression is registered on the dial. From this it will 

 be understood that its readings do not depend on the length 

 of line paid out, but on the pressure produced by the ver- 

 tical height of the overlying water. It is quite immaterial 

 what position the instrument may assume in the water, and 

 the depth registered in no way depends on tlie direction it 

 follows in going to the bottom. The figures on the dial 

 represent the pressures produced by varying depths of 



The Herbertz Foundry Cupola (elevation.) 



water in fathoms, so that readings can be taken direct with- 

 out any calculation. There is also a spring-catch to retain 

 the pointer in place, until the instrument is taken out of 

 the water and examined. After the examination the 

 catch is released and the pointer returns to zero, the 

 sounder being then ready for another cast. 



All the working parts of the apparatus are plated, to 

 protect them from the action of the sea-water, and they are 



enclosed in a brass case, having a sliding cover for inspec- 

 tion of the dial when required. The apparatus has many 

 good and useful points, and we have much pleasure in 

 recommending it. The makers are The Hannay's Patents 

 Company, Limited, of 67, Great Clyde Street, Glasgow. 



THE HERBERTZ CUPOLA. 



/'~\UR readers are doubtless aware that the iron used for 

 ^-^ making castings in a foundry is mixed with coke and 

 melted in a cylindrical furnace, called a cupola. For the 



The Herbertz Foundry Cupola (section.) 



operation to be successful there must be a strong indraught 

 of air to quicken the combustion of the coke, so as to in- 

 tensify the heat and liquefy the metal. For this purpose it 

 is usual to obtain an air blast by means of a rotary fan, 

 driven at a high speed by engine power, but a new system 

 has lately been adopted which promises very important 

 results. The new cupola was invented by Mr. Herbertz, 

 and is now being made in this country by Messrs. Tangye, 



