BAIRD &.TATLOCK (LOTsTDON) LTD. 



4826 4830 



4826 T Simmance 1 c. Pentane Standard Lamp .. .. .. .. ..330 



4827 T Simmance 2 c. Pentane Standard Lamp . . . . ..550 



4828 T Simmance 10 c. Pentane Standard Lamp .. .. .. ..770 



4829 T Candle Balance for weighing candles while burning with 40 grain weight . . . . 650 



4830 T Harcourt's 10 c. Pentane Lamp. This is the official standard for the metropolis, and 



is the standard adopted by the National Physical Laboratory . . . . . . 880 



4831 T Standard Sperm Candles, 6 = i Ib. (burning at the rate of J oz. per hour) . . per Ib. 040 



4832 T Simmance & Abady's Correction Tables for 10 c. Pentane lamp, according to the 



National Physical Laboratory formulae . . . . . . . . . . ..220 



NOTE. The Harcourt Pentane Lamp, although the only recognised standard, requires (like all lights derived 

 from combustibles), large corrections for atmospheric conditions. These corrections have been determined and 

 expressed in formulas by C. C. Paterson, of the National Physical Laboratory Messrs. Simmance & Abady have 

 compiled the tables No. 4832 so that all calculation is avoided. The ventilating hygrometer, No. 4833, is all 

 that is necessary if a barometer is available. The importance of these corrections will be obvious when electric 

 lamps are being standardised or tested by the Harcourt Lamp. 



CHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS- 



879 



