1842.] Philosophical Instruments in India. 297 



for the manufacture of philosophical instruments, which have not yet 

 suggested themselves to me ; but among these, prominently occurs to 

 me the opportunity of constructing a suferior glass for forming the lens 

 of telescopes, a desideratum, which in England opticians have sought in 

 vain, from the obstacles thereto in the way by the operation of the laws 

 of excise, while in India no obstacles of this kind exist. The materials 

 for making the finest glass are cheap and plentiful, and it is well known, 

 that the famous glass made by M. Ginnund, of which the great Dorpat 

 telescope is constructed, was made in small experiments upon less than 

 two hundred weight of materials at one time. 



For making a complete set of philosophical experimental apparatus, 

 India affords all the materials required, with the exception of glass, 

 whence it will be necessary to purchase in London all the glass chemical 

 apparatus for the electrical apparatus, receivers for air-pumps, and for 

 the lenses of the optical apparatus ; but as the expense of these articles 

 at the glass-house is but little, it will form probably but a very small 

 item in the outlay. 



With the modes of executing the proposed instruments, fitting electri- 

 cal machines and grinding lenses, I am perfectly acquainted, from hav- 

 ing made them for my own use while in England, and from having 

 had the advantage of inspecting, and using the best which have been 

 in London, and from having had the opportunity of seeing the work- 

 shops of many of the most eminent philosophical instrument makers. 



Rayacottah, 5th October, 1841. 



Manual of Chemistry. By Capt. J. Campbell, Assistant Surveyor 

 General, Madras. 



PREFACE. 



This work was planned several years ago, in consequence of the 

 difficulty which I found in procuring practical information in fitting 

 up a small laboratory for investigations in the Chemical composition 

 of rocks and minerals. Some parts have been for a long time compiled 

 as a set of notes for ready reference, and have been altered and cor- 

 rected, as further investigations and experience rendered it necessary. 

 It was my intention to have published the part upon Action of Tests, 

 but it was laid aside upon finding that the late Lieut. Braddock of 



