1853.] Report on the Geological Structure of the Salt Bange. 451 



In calculating the heights I have used for sea-level observations 

 those recorded in the Surveyor General's Office, Calcutta, as publish- 

 ed in the Journal of the Asiatic Society. Provided with one instru- 

 ment, this was the only course I could adopt. Galbraith's Barometric 

 Tables, which are considered to be very accurate, were employed, and 

 their extreme simplicity is a strong recommendation in their favour. 



The instrument employed was a Newman's mountain barometer 

 of the latest and most approved construction, furnished from the 

 Arsenal of Port William. It was safely conveyed from Calcutta to 

 Lahore, in November 1850, attached to a Palki, and from thence was 

 brought on to Maree on the Indus by Mr. Purdon, from whom I 

 received it in the middle of Pebruary 1851. There was then but 

 little leakage, and its indications seemed accurate until towards the 

 end of March, when it commenced to leak very much and became 

 quite untrustworthy. On examining into the source of the leakage 

 I found it proceeded partly from a crack which had formed in the 

 upper wooden part of the cistern, and partly from the side of the 

 tube where it passed into the cistern ; several plans were tried with- 

 out avail to stop the leakage, and at last the mercury escaped to 

 such an extent, as to admit of air passing into the tube. 



By the contact of the escaped mercury with the solder which con- 

 nected the vernier to the arm of the rack which moves it up and 

 down the scale, the vernier became detached, an accident which never 

 could happen if the arm of the rock and vernier were made out of 

 one piece of metal. It is somewhat strange that an instrument-maker 

 of Mr. Newman's celebrity, should not have guarded against the 

 possibility of an accident, such as I have recorded. 



In manufacturing mountain barometers for use in the very dry 

 climate of the north-west provinces of India, it would be highly 

 desirable that the wooden part of the cistern of Newman's barome- 

 ters should be either entirely dispensed with, or be constructed of 

 some thoroughly baked dry and tough wood. I very much doubt, 

 however, if any wood will stand without cracking, the influence of 

 the sun and hot dry winds of the Punjab in March, April, and 

 May. 



Another barometer of an old pattern without even a rack adjust- 

 ment of the vernier, and set in a round mahogany case, which was 



