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On an improved Simpiesometer, " The Tropical Tempest Simpiesometer," just 

 received in Calcutta. By H. Piddington, Sub- Secretary, Asiatic Society, tyc. 



The following Notes were by the kindness of Mr. Lepage, of the firm of Ostell and Lepage, 

 Booksellers of this city, handed to Mr. Simms, of the well-known firm of Troughton and Simms, 

 with a request that they would try the experiment indicated, and manufacture an instrument for me 

 with the improvements suggested. They have done so, and the instrument was exhibited at the 

 August Meeting of the Asiatic Society. 



There are two objections made to Simpiesometers. The first, that "they 

 disquiet people needlessly," and the second, that "they get out of order." 

 The first objection it is evident we cannot remedy, for it depends on indivi- 

 dual character, on experience, on knowledge, and on many other personal or 

 acquired peculiarities and qualities, over which we have no control. But 

 with respect to the second defect, I think I can point out to the makers of 

 these instruments, two principal sources of it; and these are, alterations in 

 the chemical qualities of the oil, and the shortness of the tube. We cannot 

 (yet) guard against any alteration of the oil, which might affect the gas ; 

 but if this occurs, it is probably through the chemical action of light upon 

 the oil. I should suggest then, as an improvement, that the glass be covered 

 with a metallic door, to open with a hinge, so that except when observed, 

 the instrument would be in darkness, where pressure and temperature 

 would operate quite as well as in the light, and the glass would be more- 

 over less liable to break. 



The next improvement is the main one, and is, I am convinced indispen- 

 sable to the efficiency of tropical Simpiesometers ; viz. instruments which 

 are to be of use for any length of time between the tropics. If Messrs. 



w ill refer to Colonel Reid's work on the Law of Storms, they will 



there see in the chapter on " Storms at the mouth of the Hooghly," p. 293 of 

 2d edition, that in 1833 in the Duke of York's Storm the Barometer fell be- 

 low 26.50 at a temperature of 79° ! and I am certain that in many storms it 

 falls at least to 27.00, with a temperature of 80° or more. 



Now if Messrs. will try in their receiver the effect of reducing 



the pressure to 27.00, and keeping the temperature at 80 or 84°, for I have 

 known it as high as this, I suspect they will find that the gas will escape 

 round the curve of the leg, and bubble up through the cistern. In a word, 

 the tube and scale are not long enough for tropical hurricane depressions ; 

 and when a ship gets through one of these, the Captain may not improba- 

 bly find that his Simpiesometer does not act so well as before, and thus the 



