Mr. Daniell on the Barometer. 91 



for any faults in its original construction? or its indications, 

 which are corrected for adventitious circumstances ? Is it cor- 

 rected for capillarity ? for temperature ? or for any variation in 

 the level of the mercury in its cistern ?J If it be a new barometer, 

 is it of the siphon or cistern construction. If of the latter," what 

 are the relative capacities of its tube and cistern 1 what the dia- 

 meter of its tube ? Is there any and what difference between its 

 indications, and those of the old instrument ? A comparison of 

 the utmost moment. The only criterion by which we may con- 

 jecture that a new instrument has been substituted for the old 

 one is, that the height is now registered to thousandths instead 

 of hundredths of an inch. But will it be believed that the coun- 

 cil of the Royal Society would suffer such gross negligence to 

 appear not only under the sanction of their " order," but after 

 all the pomp and circumstance of a committee specially appointed 

 to superintend the necessary arrangements ? The fourth and 

 fifth columns contain the indications of the thermometers. The 

 latter is headed M Thermometer Without." Whence, I presume, 

 it is fair to infer that the other is, as before, " Thermometer 

 Within." And yet this is entitled, in some places, M Six's Ther- 

 mometer," and in others, H Register Thermometer." And we 

 are told in the first note, " Six's thermometer deranged, and a 

 horizontal register thermometer substituted for it." But then 

 what does it register ? There is but one observation in the day 

 recorded ; it cannot be the maximum, because in many cases the 

 " thermometer without" is higher. It cannot surely be the 

 minimum, for who would take that from an interior thermometer 1 

 However, before three months have elapsed, note the second 

 informs us H Register thermometer deranged." Then comes 

 an hiatus valde dejlendus of a month, and we return once more to 

 Six's thermometer and two observations per day — but how re- 

 paired, and where placed, we are not informed. 



Thai- sixth column is entitled " Daniell's Hygrometer," and 

 contains, I presume, though nobody but myself is bound to con- 

 jecture this, the dew-point. 



The seventh column records the M degrees of moisture," but 

 whether calculated from the same instrument, or from any other 



