Remarks on Self -Registering Thermometers. 303 



King (in last No. p. 118,) are pleased to call a Meteorological 

 Journal " the veriest drudgery in science !" 



The thermometer described by this gentleman (Mr K.) is, 

 it will be observed, only a maximum one ; and notwithstand- 

 ing any practical defects, it might perhaps replace well the 

 maximum thermometer of Rutherford, which is very liable to 

 have its index entangled in the mercury. Experience alone 

 can determine how far this adoption might be advisable. One 

 plan I originally thought of, for remedying the necessity of 

 raising the temperature of the column of mercury till it joined 

 the reservoir, and then suffering it to assume the external tem- 

 perature, was good in theory, but without superior workman- 

 ship would not succeed in practice. It consisted in having the 

 air so thoroughly expelled from the instrument, that when the 

 top of the thermometer was raised, by a gentle shake the mer- 

 cury might run down the tube and join the rest, or that, if the 

 bulb was raised, it should run up to the cistern at the top, and 

 when reversed the column would be continuous. I think that 

 it might be thoroughly freed from air by allowing the fluid 

 first to fill the tube and bulb, and then boiling it in the globu- 

 lar cistern, allowing the air to escape by a capillary orifice left 

 in the top of the cistern, which would at the same moment be 

 closed with the flame of the lamp. Good thermometers, if 

 the diameter of the bore be at all considerable, permit the mer- 

 cury to flow readily from the bulbs, and return to them with 

 a click. In the present case, therefore, we should make first] 

 rate workmanship necessary to the principle of the instrument, 

 and a tube with large bore, which necessarily destroys the de- 

 licacy of the instrument, on which I should principally rely 

 for the superiority of thermometers which do not require an 

 index. 



The minimum thermometer of Rutherford is certainly a 

 very excellent instrument, and when not subjected to such 

 sudden changes of temperature as to divide the column of al- 

 cohol, is not liable to be out of order. Six's, which registers 

 both extreme heat and cold, is very imperfectly constructed, 

 and is often fallacious in its indications. The one which I 

 daily use is by one of the first London makers, yet it is fre- 

 quently out of order, and follows imperfectly the atmospheric 



