L. CASELLA'S CATALOGUE 



The Boylean lariotti Barometer, or Patent 

 Mercurial Pocket Standard Barometer. In 



this elegant and interesting arrangement the 

 mercury is raised from the cistern to the fidu- 

 cial or zero point by means of a screw, a portion 

 of air being admitted and compressed at each 

 observation. The body and cistern may be 

 separated at pleasure for convenience of carriage 

 in the pocket or knapsack. As a portable 

 barometric test or standard instrument for 

 mining purposes, or measuring any extent of 

 mountain heights, it is believed to have no equal. 

 For fig. and description, see addenda. 



FIG. 85* 



FIG. 85. 



89. Ozonometer (DE. SCHONBEIN'S), consisting of strips of paper prepared with iodide 



of potassium and starch. The papers are to be suspended so as to be exposed 

 to the free access of air, but sheltered from wet and the direct rays of the sun ; 

 when affected by ozone, they become tinged, the intensity of which is measured 

 by a graduated scale of twelve tints, which accompanies the ozonometer. 

 L. CASELLA is the sole agent for Dr. Schonbein's ozone test papers. In case 

 to last one year. . . "r ..... ... , . . 066 



90. Dr. MOFFATT'S OZONOMETEE . ,. . . . 086 



91. Sedan's Ozonometer . . -* . . . 086 



92. OZONE CAGE of fine wire gauze, as recommended by Sir Jas. Clark . 12 6 



93. Smaller Size, ditto, for travellers . . . . . 12 6 



94. Casella's Forms for Registering Ozonometer Indications . 016 



95. CASELLA'S FOBMS FOE EEGISTEEING METEOEOLOGICAL OBSEEVATIONS, with 



concise remarks and instructions, in twelve monthly forms for one year 



040 



96. Portable Meteorological Register and Note Book (STBACHAN'S), with weather 



diagrams, tables, and instructions, second edition . . 2 6 



