44 REPORT 1871. 



to elicit an opinion whether the results likely to be obtained would be of sufficient 

 importance to warrant a more elaborate discussion of the entire series of observa- 

 tions with a view to future publication. 



Paste Photographique. By the AsBi: Moigno. 



An Account of a New Photographic Dry Process. By R. S utton. 



Heat. 



Description of Eccperiments made in the Physical Laboratory of the University 

 of Glasgow to determine the Surface Conductivity for Heat of a Copper Ball. 

 By Donald M'Faelane. 



The experiments described in this paper were made under the direction of Sir 

 W. Thomson dming the summers of 1865 and 1871. A hot copper ball, having a 

 thermoelectric jimction at its centre, was suspended in the interior of a closed 

 space kept at a constant temperatiu-e of about 16° Cent., the other junction was 

 kept at the temperature of the envelope, the circuit was completed through a 

 mirror galvanometer, and the deflections noted at intervals of one minute as the 

 ball gi-adually cooled. 



The method of reducing the observations was explained at length. The difference 

 of the Napierian logarithms of the differences of temperatures of the junctions, 

 indicated by the defections, divided by the intervals of time, gives the rate of 

 cooling ; and this, mLiltiplied by a factor depending on the capacity for heat of the 

 ball and on the extent of its surface, gives the quantity of heat emitted in gramme 

 water units in the unit of time per square centimetre, per 1° of difference of teni- 

 peratm'es. Formulae were given which express the results of the experiments very 

 closely, and a table calculated by them exhibits the rates of emission for every 5° 

 of difference throughout the range. 



The first and second series had a range of from 5° to 2o° only, which was too 

 small to give decided results ; but the third and fourth series, made with a polished 

 copper surface and a blackened surface respectivelv, gave variations in the emissive 

 power from -000178 at .5° diff. of temperature to •000226 at 60° difl". for the polished 

 sm-face, and from -000252 at 5° diff. to -000328 at 60° diff. for the blackened sm- 

 face ; and the emissive powers of the two surfaces exhibit throughout a nearly 

 constant ratio to each other of about -694. 



On a Respirator for Use in Extinction of l<ires. 

 By William Ladd, F.R.A.S. 



This instrument comhines the advantages of the charcoal and the cotton-wool 

 respirators. The respirator is intended to be fitted on the heads of firemen, and it 

 will enable a fireman to enter into the midst of any smoke, however dense. There 

 is sufficient protection for the eyes, by means of glasses. The results of an experi- 

 ment with the respirator have been stated by Prof. Tyndall. In a small cellar-like 

 chamber, fm-naces containing resinous pine-wood were placed, and the wood being 

 lio-hted, a dense smoke was generated. In this room. Prof. Tyndall and his 

 assistant, using these respirators, remained for more than half an hour, when the 

 smoke was so dense and pungent that a single inhalation through the unprotected 

 mouth and nostrils would have been perfectly unendurable. The instrument has 

 been tested by Capt. Shaw, chief officer of the Metropolitan Fire Brigade, who 

 has taken very great interest in perfecting it, by attaching to it suitable hoods. 



