284 Mr. Bevan on Measuring the Force of Pressure. 



Gloucester. I had long ago discovered iodine in both, the 

 quantity in the former being minute, and in the latter im- 

 portant. I also found the muriate of ammonia in both: but 

 lest Dr. Daubeny should treat a mere assertion as a posthu- 

 mous claim, my evidence will be found in the announc^ement 

 eni'olled in the columns of the " Gloucester Journal" and 

 other newspapers; and this is also recorded in the second 

 edition of my "Manual of Experiments illustrative of Chemi- 

 cal Science*." At the period in question, bromine had not 

 been discovered ; but since that time I discovered both iodine 

 and bromine in the brine springs at Ingestrie, and the fact 

 vi'as communicated to Earl I'albot six months ago. I also 

 found bromine in a portion of w^ater which 1 brought from 

 the Salines at Bex in Switzerland ; the presence of iodine in 

 them had been previously announced. 



In the former case I might also have referred to Dr. Baron 

 of Gloucester, and others ; but I trust I have said quite enough 

 to substantiate my claims to priority, and may merely now 

 add, that I repeated a number of interesting experiments some 

 months ago on the Breakwater in Plymouth Sound, which 

 seemed to me an eligible station for the eudiometrical exa- 

 mination of the incumbent marine atmosphere; and it maybe 

 here merely necessary to mention that I detected the presence 

 of carbonic acid gas, muriates; and received distinct evidence 

 of both iodine and bromine. 



I am, Gentlemen, yours, &c. 



8th September, 1829. J. MuRRAY. 



XLI V. 0» Measuring theForce of Pressure. By B. Bevan, Esq. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, 



TO the practical mechanic, it is often desirable to ascertain 

 the actual pressure produced by various machines and 

 instruments, and it is often desirable to do this in spaces too 

 small to admit the ordinary machines for measuring the force 

 of pressure ; such, for instance, as powerful screw and hy- 

 draulic presses, and other machines of that nature. To the 

 screw, in all its modifications, there always befongs a very con- 

 siderable portion of friction at present not well determined : — 

 the proportion of friction to the gross pressure in the hydraulic 

 press has not been satisfactorily ascertained. 



Having lately discovered a mode of measuring the actual 



• Published by Messrs. Longman and Co. 



pressure. 



