945 



Some consecutive experiments made with illuminating gas, resulted in con- 

 sumption of potash-lye : 



12 -0 cc. = 1-36 per cent. 



l2-lcc. = l-37 



ll-8cc. = l-34 



The apparatus, of course, is only intended for ascertaining small quantities 

 of carbonic acid, such as is the case with illuminating gas. The other com- 

 ponent parts of gas are of no perceptible influence on this method. 



The analyses mentioned prove this sufficiently in order to secure for a 

 method a certain adoption in practice, which recommends itself just as well 

 by its trustworthy results, as by easy and speedy execution. 



27S8a. Special set of Observatory Standard Meteoro- 

 logical Instruments. Negretti and Zambra's special selection 

 of standard meteorological instruments for a first class observatory 

 station, consisting of: Standard barometer, maximum thermo- 

 meter, Rutherford's minimum thermometer, mercurial minimum 

 thermometer, hygrometer, wet and dry bulb, solar radiation ther- 

 mometer, terrestrial radiation thermometer, Robinson's anemometer, 

 rain-gauge (Glaisher's pattern). Negretti and Zambra. 



2796a. Standard Barometer with Electrical Adjust- 

 ment. Neyretti and Zambra. 



This is a tube dipping into a glass cistern of mercury, fitted with a vertical 

 adjustment screw. Through the top of the tube a platina wire is passed and 

 hermetically sealed. The cistern has a metallic connexion, so that by means 

 of copper wires (in the frame) a galvanic circuit is established ; another con- 

 nexion also exists by a metallic point dipping into the cistern. The circuit, 

 however, can be cut off from this by means of a switch placed about midway 

 up the frame. On one side of the tube is placed a scale of inches, with a 

 circular vernier, divided into 100 parts, connected with the dipping point and 

 working at right angles with the scale. 



279Gb. Negretti and Zambra's Standard Barometer, 



constructed on Fortin's principle, proved to be the most reliable 

 arrangement yet introduced. The level of the mercury in the 

 cistern being adjusted previous to each observation to a fixed ivory 

 zero-point, loss of mercury from leakage or oxidation is of little or 

 no importance, and does not affect the accuracy of the readings. 

 The tubes are of varying internal diameter, and are filled with 

 pure mercury, very carefully boiled in the tube to perfectly expel 

 all air or moisture. Negretti and Zambra. 



2796c. The Gun Marine Barometer, constructed by 

 Negretti and Zambra for special use in Her Majesty's navy, and 

 now the adopted Admiralty pattern. It differs from barometers 

 hitherto made by having its tube packed with vulcanised india- 

 rubber, which checks vibration from concussion, thereby doing 

 away with the necessity of unshipping the barometer during gun 

 firing. 



See Admiral Fitzroy's report, 9th number of the Meteorological 

 Papers, issued by the Board of Trade. Negretti and Zambra. 



39508. 3 



