1865. 11 [Trippel. 



in an air column, leaving consequently a surplus of 35.2 — 6.74 = 

 28.46 feet in the combustion canal, K. 



3Jiina(jement of the Furnace. — We have here omitted entirely all 

 calculations regarding resistances, etc., as more or less irregularities 

 in the practical working cannot be avoided, and as, consequently, such 

 calculations would be quite illusory. 



It will be, however, of much benefit, to use in connection with the 

 furnace a multiplicator manometer, of which we give a sketch with 

 the furnace plans. 



The manometer has been known for a long time as a useful instru- 

 ment to measure the pressure of blast produced by blast machines. 

 The latter is generally of a higher pressure, so that minute divisions 

 on the manometer scale are of not much importance, and the usual 

 instrument is rather inconvenient, as it needs very close observa- 

 tions to see the oscillations corresponding to small diflFerences in the 

 pressure. For very low pressure, however, the usual manometer is 

 not admissible, as it would be diflScult, if not impossible, to determine 

 such small differences as parts of an inch in a water column. It was 

 Peclet who first proposed a manometer, which answered the purpose 

 of measuring very small pressures; Mr. Schinz improved the same 

 materially, and presents it in the following construction : 



Fig. I, to in, represents a sheet-iron box, y, of 20" length, 6" 

 breadth, and 4" height, with a separate capsule of 4^" diameter 

 within, which reaches nearly to the bottom of the box, and is open 

 on both ends. 



The cross section of the box, inclusive the capsule, is 20.6 = 120 

 square inches; the cross section of the capsule is \. (4j''.314) = 

 15,896 square inches. 



The highest pressure of the wind is calculated in this case to 2" in 

 a water column. If we have that pressure, the height of the water 

 in the box will be 1", and in the capsule 3". As soon as this 

 pressure ceases, the water in the box will rise in proportion of 

 120: (2 -f 15.896) = 0.2649" (as the capsule contains 2.15896 

 cubic inches), above the original water-level in the box, and at its 

 sinking, the water in the latter rises 0.2649 inches. If we lower the 

 level by a pressure of 2", the water in the capsule consequently rises 

 only 2 — 0.2649 = 1.7351". 



This movement is now to be transferred to a mechanism which 

 shows this difference multiplied on a circle or a part of it. This me- 

 chanism consists simply in a swimmer, a, from which a silk thread, 

 J, goes over a roller, c, and is counterbalanced by the weight, d. 



VOL. X. — C 



