Mechanical Science. 169 



8_ 

 100 + * 100 11* 



11 + 0.03 * 11 11+0.03* 



the increments may be considered as proportional to the quotient, 



* 



, and the elastic force may be expressed by the formula 



nx 



F = 760 M xlO 



11 + 0.03* 



m being a constant coefficient, and 760 m the pressure of the atmos- 

 phere ; this formula, by employing logarithms, becomes 



Log F = log 760 + — - ^— — . 

 & b J- 11+0.03* 



If F be known by experiment, n will be obtained by resolving the 



preceding equation, which will give 



7i = ■ (log F — log 760 m ). 



Now, if the values of n, which I call the logarithmic modulus of 



the elastic force of steam, be taken according to the table of elastic 



forces drawn up by the Institute, and inserted in the Traite de 



Physique of M. Pouillet, the mean value of n will be found == 0.17 ; 



the other values differing but little from it, the formula then 



becomes 



T ^ , „™ 0.17* 



Log F = log 760™ + u+omx - 



In a memoir which I presented to the Institute, in the month of 

 February, 1827, and which was referred to the examination of the 

 committee charged with investigating high temperatures in steam- 

 engines, I shewed how the modulus of steam of other liquids might 

 be found, and their density calculated therefrom ; and I found that 

 the maximum of the elastic force of water takes place at a tempera- 

 ture of about 770°, where its density is nearly equal to that of the 

 liquid, the pressure amounting to more than 4000 atmospheres. 



12. Destruction of Vermin in Ships by Steam. — By letters from 

 India, it appears that the application of steam has been found won- 

 derfully efficacious in cleansing ships from vermin, and especially 

 the white ant. A steam-boat (the Comet) was placed alongside a 

 merchant-vessel, and steam from its boiler conveyed by a very 

 simple system of pipes into the hold of the latter, the apertures 

 to which were closed as well as they could be. The operation was 

 continued for several hours ; and there is no reason to believe that 

 it was not effectual, and will prove a valuable process in the navy. 

 Besides the t direct object of cleansing the ship, another advantage 

 accrued, from the discovery of every leaky place existing, by the 

 oozing of the water through them, in which way leaks were made 

 manifest, that could not be found out otherwise. The expense is 



