Do^rine of Heaf, xuith RefpeiJ to denfe and elaftic Fluidti 23 



It will be always advifeable to make the length of the defcending branch of the fyphon 

 exceed that of the afcending one, as much as circumftanccs will admit, and to let th« 

 loweft part of it be made of a conical divergent form : the velocity of the current will be 

 thus encreafed, the veflel will be fooner filled, and the deprefllon of the columns will be lefs 

 liable to happen from very flight imperfedlions in the valves. 



I am, SIR, 



Your humble fervant, 

 Dalton, Feb. 21, 1801. . WILLIAM CLOSE. 



'^CORRECTION. 



There was a flight omiflion made in one paragraph of the letter before this, which may 

 cafily be correfted. Pleafe to look for the following words at the beginning, page 547. 



If the connexion between the velTel and fyphon was made by two tubes inferted into the 

 [horter branch one immediately above the other, the end of the lower turned againft the current, 

 and the end of the higher turned from it, the ftream, &c. Infert the words with the line 

 under them. 



On the Do3rine of Heat ; particularly with regard to the States of denfe and clafiic Fluidity tn 

 Bodies, In a Letter from Mr. Joseph Astley. 



• To Mr. NICHOLSON. 

 SIR,, 



HAT the folid, liquid, and aeriform modifications of bodies depend on nothing more 

 than the different proportions of caloric with which they are direftly combined, is an 

 opinion fo attraQive, from its apparent fimplicity, and fo clofely aflbciated with our moft 

 elementary notions refpefting the phyfical laws of nature, that a degree of prejudice may 

 perhaps be excited in many by the mere fuggeftion of a doubt upon the fubjed. Thofe 

 intimate with chemical theories have learned, however, that the apparent fimplicity of a 

 doftrine is as frequently the refult of an imperfeft as of intire comprehenfion of the fubje£l: 

 which it regards, and that our folicitude to eftablilh the conformity of particular phenomena 

 too often leads us to admit inconfiftencies into our general principles of phyfical economy. 

 The new lights which have been lately thrown on fevcral of the phenomena in which 

 evaporation is concerned, particularly on thofe of meteorology, have be^ fufficlent to 

 3 create. 



