296 Dr. Apjohn on Wollaston's Thermometer. [Oct. 



Two other measurements have since been made with the 

 therm, barometer which differ very widely indeed from the 

 barometrical determinations. The one was of the greater Sugar 

 Loaf, the other of Douse Mountain. We will give the particu- 

 lars. On Aug. 12, within a quarter to 11 o'clock, a. m. the 



instrument stood near Col. Wingfield's lodge at 212 + ^ ther- 

 mometer 62, and same day on the summit of the greater Sugar 

 Loaf within 20 minutes of two, p. m. it stood at 209 + -*, 

 therm. 60; and same day, also, on the top of Douse, 31 minutes 

 past four, it stood at 207 + — 5 , thermometer 54. From these 



data, it follows that the tabular heights of these mountains 

 respectively are 1579*446 and 2326-33 feet. To these numbers 

 a correction must be applied which has not been hitherto 

 adverted to. In the interval between the first and the succeed- 

 ing observations, a barometer at Dr. Stoke's house, Harcourt- 

 street, rose from 30 to 30*05, where it continued for the remainder 

 of the day. Now as this increment of pressure must have pre- 

 vented the due fall of the boiling point on the Sugar Loaf and 

 Douse, a compensating correction must be applied to the tabular 

 heights given above. This is easily done. For as *6 of an inch 

 on the barometer corresponds very nearly to the 212th degree ; 

 that is, to 330*006 feet (see table) *05 of an inch will give l-12th 

 of a degree, which is equivalent to 44*25 feet. By adding this 

 to 1579*446 and 2326*33 feet, we shall have 1623*696 and 

 2370*58 feet for the true tabular heights of the Sugar Loaf and 

 Douse. When, to these numbers corrected for temperature, 

 .15-5 feet be added (the height of the lowest station over low 

 water mark), we shall get for the true heights of the Sugar Loaf 

 and Douse 1737*137 and 2514-28 feet respectively. The height 

 of the Sugar Loaf as determined by Dr. Taylor and Mr. Weaver, 

 according to the barometrical method, is 2004 feet, and that of 

 Douse, as similarly determined by Mr. Griffith and Mr. Weaver, 

 is 2392 feet. The elevation, then, we give Douse, is about 122 

 more than that assigned it by these gentlemen, and that we give 

 the Sugar Loaf about 267 less. It is difficult to reconcile dis- 

 cordancies of such magnitude. It is remarkable, however, that 

 we make the excess of the height of Douse over that of the Sugar 

 Loaf nearly twice as great as that deduced from the barometrical 

 results. Now an error of this amount, I am confident, could not 

 have occurred in our observations. I am, therefore, I confess, 

 at present disposed to account for the want of correspondence 

 between our measurements by some error in the barometric 

 determinations. It is proper to observe here, that all the above 

 observations were made conjointly by me and my friend Mr. W. 

 Stokes. 



