342 Topographical Remarks regarding Afghanistan. 



The practice of inoculation is common, especially amongst 

 the Hazaras, but vaccination has not as yet been introduced. 



Cholera prevailed to a great and fatal extent in 1826, and 

 small-pox now and again commits its ravages amongst the 

 inhabitants. 



On the Construction and Management of delicate Balances, 

 and a new method of Weighing. By Captain J. Campbell, 

 Assistant Surveyor-General, Madras Establishment. 



To the analytical chemist a delicate balance is an instru- 

 ment of the utmost importance, the whole of the results ob- 

 tained in his researches being estimated by its mechanical ac- 

 tion, and even the operative manufacturing chemist depends 

 upon its indications for the correct knowledge of the values 

 of metallic ores, and the purity of the precious metals. 



In India these instruments are not made for sale, and any 

 person requiring one, must either submit to the delay of 

 ordering it from England, or else make it up himself ; while 

 the price charged in London for them is very high ; if a fine 

 one, never under 20/ or 30/. 



If the mode of adjusting a balance is not perfectly under- 

 stood, it becomes nearly useless ; but to make the necessary 

 adjustments, a considerable degree of mechanical skill and 

 knowledge is required, and therefore in England chemists sel- 

 dom trouble themselves with it, but leave it to the makers; few 

 authors in consequence are acquainted with this practical 

 operation, and the directions generally given in works are of- 

 ten based upon false principles. 



In India any one who has picked up a knowledge of me- 

 chanical arts may, with the assistance of a good native work- 

 man, make up an excellent instrument at a trifling expence ; 

 and Lieutenant Braddock has shewn in the Madras Journal,* 

 that instruments so made are not at all inferior to those which 

 * Madras Journal, vol. ii. page 86. 



