TRANSACTIONS OP THE SECTIONS. 



49 



Instructions for the Graduation of Boiling-point Thermometers, intended for 

 the Measurement of Heights. By J. Welsh. 



Let the thermometer be in the first instance filled with a suiRcient quantity of 

 mercury to allow the point 82° Fahr. to be where the point 212° is desired ulti- 

 mately to be. Let a chamber be made at the top of the tube about 3 inches 

 above the point 212° ; or, if the thermometer is required to have a chamber at the 

 top when finally completed, let there be two chambers made with sufficient space 

 between them to allow of the tube being there sealed by a blowpipe flame. By 

 comparison with a standard thermometer, set off the points 82°, 72°, 62°, 52°, 

 42° (but not 32°). The scale may then be divided, adopting the mark 82 as 

 corresponding to 212-00 ; 72 to 20r87 ; 62 to 19174 ; 52 to 181-61 ; 42 to 171-48. 

 The graduation of the scale should then be verified by comparison with a standard 

 thermometer at different points from 37° to 87° Fahr., and a table of errors of 

 graduation thus obtained. A sufficient quantity of mercury must now be separated 

 from the main mass until the top of the column stands in boiling water at the 

 proper reading. The superfluous mercury having been lodged in the upper chamber, 

 may be removed by sealing up the tube between the two chambers. If it is not 

 possible to detach exactly the proper quantity of mercury to make the column stand 

 at the true temperature of boiling water, the difference should be added as a further 

 constant correction to the table already found by comparison with the standard. The 

 following determination of the corrections to a thermometer, constructed on this 

 principle by Messrs. Negretti and Zambra, will serve as an example of the accuracy 

 which may be attained by this method. — • 



On Barometrical and Thermometrical Observations at Scarborough. 

 By Captain Woodall, M.A . 



CHEMISTRY. 



On the Composition of Paraffinefrom different sources. By Thomas Anderson-, 

 M.D., F.R.S.E. Regius Professor of Chemistry in the University of Glasgow. 

 Some seven years since tlie author commenced the investigation of Rangoon petro- 

 leum, but being at the time engaged in other researches, the subject was abandoned 

 after some experiments and analyses of the paraffine it contains had been made. 

 More recently his attention had been directed to this substance in examining the 

 parafBne obtained during the distillation of coal. He found that Boghead coal yields 

 two distinct kinds of paraffine, one highly crystalline after fusion, the other a granular 

 1856. 4 



