42 L. CASELLA'S CATALOGUE 



152. POBTABLE EOSEWOOD BAEOMETEB, handsomely fitted up, inlaid with pearl, plate- 



glass in front, double rack- work, and verniers reading to the 100th of an inch 



6 6 to 8 8 



153. Portable Barometer, extra size, tuhe 0'4 inch internal diameter, and cistern 2'75 



inch ditto, ivory plates, with verniers reading to 100th of an inch, carved top 

 and sides ; thermometer in front covered with plate-glass, floating gauge, for 

 plain standard adjustment when required (fig. 153, p. 41) . 8 10 



154. Portable Barometer^ with large tube and cistern, the graduation of the scale 



compensating for variation in the level of the mercury in the cistern ; hand- 

 somely engraved ivory plates, with German silver mountings, and double 

 vernier, each reading to the 100th of an inch ; combining every excellence of 

 which this description of barometer will admit (Jig. 154, p. 41) 4 10 



155. POETABLE BAEOMETEE, plain pattern, thermometer in front, ivory plates, rack- 



work, and vernier reading to the 100th of an inch, portable screw and plate 

 glass, in rosewood or mahogany (fig. 155, p. 41) . . 2 10 



156. Portable Barometer, with open face and ivory plates, vernier reading to 100th of 



an inch ; thermometer at side, and portable screw ; in rosewood, oak, maho- 

 gany, etc., being a good and hardy instrument, adapted alike for home use or 

 transmission to all parts of the world (fig. 156, p. 41) 150 



157. Agricultural or Cottage Barometer^ expressly designed by L. CASELLA as a cheap t 



portable, and popular weather glass, accompanied with plain description and 

 instructions (fig. 188, p. 47) . . . . . 12 6 



For barometers of this construction, see also Nos. 188, 189, and 190. 



158. Long Range Barometer (DESCAETES). This interesting arrangement consists of 



a syphon tube filled with mercury, and having the column of ordinary length, 

 the upper part of the tube and short limb being say half an inch in diameter ; 

 to the latter a length of tube is united, extending to the top, the interior 

 diameter being, say one-eighth of an inch. This tube and lower limb of the 

 instrument being partly filled with a fluid of very light specific gravity, the 

 rise and fall of the mercury is shown by it, but extended in length in propor- 

 tion to the difference in capacity of the two tubes. In this way the ordinary 

 barometric inch may be extended to from seven to ten inches, which being 

 moderately subdivided, the barometric action or changes during a storm are 

 often visible. This instrument, however, is not very portable, and should only 

 be carried by hand from place to place \* - . . 2 10 



CIRCULAR OR DIAL BAROMETERS. 



This popular and interesting arrangement of household instrument was first designed 

 by that able philosopher Doctor Hook, who took great pains to make it perfect, so much 

 so, that had his plans been carried out with fair progressive improvement, and the 

 instrument been of a slightly more portable character, any other arrangement of 

 weather indicator for general use might almost be considered superfluous ; the clear 

 and expanded graduations on the dial, as well as its well-known 'response to the simple 

 tap so frequently given " to see which way the mercury is going," is familiar to all. 



Not only did the Doctor attach a thermometer to it, but a hygrometer also, and 

 even a level for the purpose of carrying out his arrangement with greater delicacy ; 



