OF METEOKOLOGICAL INSTRUMENTS. 



11 



FIG. 30. 



jury in awarding the only prize medal for registering meteorological instruments to L. 

 CASELLA, and since then their adoption may be called universal. Thus, on this 

 principle only, are those now made that are used by the faculty in the delicate investiga- 

 tions of the temperature of the body. It is exclusively used in registering thermo- 

 meters for travellers, as well as for mines, deep wells, on ship-board, and indeed in any 

 position in which portability and a true and reliable registration of temperature is 

 required. The great advantage of this arrangement consists in the index, being 

 formed of a small portion of the mercury itself, which is detached from the rest and 

 made of any required length, according to the kind of thermometer to which it is 

 applied ; thus, for stationary instruments, it is kept sufficiently long to be set by merely 

 lowering the bulb, whilst in others it is made short, so as to retain its indication in 

 whatever position the thermometer may have to be used, whether erect or inverted. 

 Thus, as a medical thermometer for clinical investigations, no other arrangement is of 

 any service (see 'JNos. 127 to 130), whilst for safely of transit also, this principle leaves 

 nothing to be desired. 



28. Maximum Thermometer^ for ordinary registration ; engine divided on the stem 



and indelibly figured on CASELLA'S improved porcelain scale, 'which effectually 

 resists frost and all effects of 'weather (fig. 28, p. 10) . 100 



29. SOLAS RADIATION THEBMOMETEE, maximum, with black bulb ; tube divided and 



figured on the stem, and enclosed in glass shield for protection (fig. 29) 



100 

 For oilier maximum thermometers, see Nos. 30, 46, 47, 48, 128, 176, and 204. 



Directions for Using the Maximum Thermometer. Suspend the instrument by means of 

 the brass loops attached to the back, so as to keep it fairly horizontal, as shown inj/zp. 28, p. 1C. 

 To set the index, disengage and lower the bulb end to allow the detached portion of mercury to 

 approach the rest, which it will do within about one-quarter of a degree. On an increase of 

 temperature the mercury will rise as in an ordinary thermometer, and continue to do so as long 

 as the heat increases, propelling the detached portion to whatever extreme the heat may attain . 

 On a decrease of temperature the mercury will contract and recede in the usual manner, leaving 

 the detached portion to indicate the highest temperature, which it does at the end furthest 

 from the bulb. 



