1837. J Experimental Self-Registering Barometer. 337 



IX. — Account of the Construction and Operation of an Experimental 

 Self-registering Barometer. — By Wm. Gilchrist, Esq. of the Madras 

 Medical Establishment. 



In my communication respecting the Self-registering barometer 

 published in No. 16 of the Journal, page 68, I mentioned with respect 

 to the float which regulates the motion of the tube, that, "if this float 

 " be sufficiently large to buoy up the tube, the balance part of the ap- 

 " paratus may be laid aside altogether, and the weight below the cis- 

 " tern, acting on the principle of ballast, will preserve the tube in the 

 " perpendicular." I have fitted up a barometer on this principle. It 

 has been in operation the last two days, and I have the pleasure to 

 state that it proves most satisfactorily the correctness of the principle 

 stated in the above quotation. I fear that a sketch of a plan of a baro- 

 meter on this principle, could not be lithographed in time for the issue 

 of No. 17, of the Journal now due, otherwise would send one. In the 

 mean time, however, it will be satisfactory to those who wish well to 

 the advancement of meteorology, to be informed that a barometer, of 

 so simple a construction as the one alluded to, can be made, thit will, 

 with scientific correctness, make a perpetual record of the varying 

 pressure of the atmosphere. 



In fitting up the barometer referred to, I purposed merely to test the 

 correctness of the principle, without reference to accuracy in the de- 

 tails of construction— in other words simply to ascertain whether the 

 instrument would work. The tube portion consisted of a four-ounce 

 glass stopper vial, by way of expanded top, cemented by means of 

 bees' wax to a common barometer tube, the closed end of which was 

 previously cut off. Presuming that those who interest themselves in 

 meteorology would desire to test this principle, in the like easy man- 

 ner, I will mention somewhat in detail the fitting up of the instrument, 

 as otherwise one or two failures may occur before success be attained. 

 In order to cement the vial and tube together, the mouth of the former 

 and one end of the latter ought to be coated with melted wax — when 

 cold, the tube is to be pushed about half an inch into the mouth of the 

 vial and retained perpendicularly—then about four inches of the tube 

 and one inch of the vial are to be coated with wax — applied in the 

 fashion of paint— and when one is cold, successive coats are to be ap- 

 plied, until a body of wax has accumulated, sufficiently strong to keep 

 the vial and tube firmly attached. It is essential to apply the wax 

 coat after coat in the manner stated— as I found the applying it in the 

 manner of casting did not make an air-tight joint. When the wax is 



