IX. OZONOMETFKS. 595 



india-rubber tube is removed, and the sucking at the upper end of the burette 

 resumed, -when, in consequence, the globular vessel is emptied. The con- 

 nexion of the burette with the sand is closed during the operation of filling. 



The evaporating vessel has a surface area of one square decimetre. 



To exclude, as much as possible, the influence of the temperature, the 

 evaporating vessel is enveloped in some bad conducting material. 



The sensitiveness of the instrument is so great that a little dry sand, or a 

 piece of blotting paper, or the fraction of a drop of water, put upon the surface 

 of the evaporating vessel is immediately indicated by the water column in the 

 burette. 



2903. Atmometer or Evaporimeter, for determining the 

 quantity of water e vaporizing from the surfaces of waters as well 

 as from different sorts of soil. Professor Prestel, Emden. 



2904. Apparatus for the direct determination of the tension 

 of aqueous vapour in the atmosphere, constructed in the year 

 1868 by Dr. Geissler, of Bonn, according to the instructions of the 

 late Prof. Schulze, professor of chemistry in Rostock. 



Professor Matthiessen, Rostock. 



The U-shaped tubes serve for the reception of the mercury. The absolute 

 vapour tension of the atmospheric air enclosed in the flask-shaped vessel is 

 directly determined, at the differential barometer, through absorption of the 

 vapour by concentrated sulphuric acid, which is introduced for that purpose. 



IX. OZONOMETERS. 



2905. Ozonometer, for the determination of the amount of 

 ozone in a measured volume of air by means of an aspirator, 

 invented by the Contributor and described by him in a paper read 

 at the meeting of the British Association in Birmingham in 1865. 



John Smyth, Jr. 



It consists of a box-wood tube or cylindrical box, about two inches long 

 and two inches in diameter, one end of which is closed, except in the 

 centre, where it is pierced by a quarter-inch tube communicating with 

 the aspirator ; the open end is covered by a lid or second box of the same 

 material, which is so large as to slide over the first, and is also pierced by a 

 quarter-inch tube, Avhich, when the ozonometer is arranged for an experi- 

 ment, directs the air against the centre of the test paper stretched across the 

 open end of the inner or first box, and is secured there by an india-rubber band 

 lying in a groove. 



2905a. Schonbein's Ozonometer, rendered self-recording. 

 An instrument for exposing each hour a fresh piece of Schonbein's 

 ozone test-paper to the influence of the atmosphere. 



R. C. Cann Lippincott. 



Two cylinders (one large, the other small) are enclosed in boxes, the openings 

 of which are guarded by india-rubber lips. The boxes are 2^ inches apart. 

 The large cylinder is moved round 2^ inches each hour by means of a driving- 

 shaft attached to the clock. A strip of test-paper, about 5 ft. long and f of an 

 inch wide, is rolled round the small cylinder, the free end of it being fastened 

 to the large cylinder ; 2^ inches of paper are thus exposed to the influence of 

 the atmosphere. 



Pp 2 



