From their unimpassioned character, their slow and quiet habits, their delicate appreciation of touch, and their untiring application, it is bable that a clever Native, if once taught properly the art of dividing the circumference of a circle, might very probably surpass the best effects of the most celebrated workmen of London.

It is supposed by many, that modern discoveries in Optics have improved refracting telescopes by the lenses being better made; but such is not the fact, the lenses of the present day are not in the least better than that Galileo and Heygens were able to make, and it is probable there is hardly a Chinese workman, who does not possess a great deal more skill in polishing a lens, than the best optician in London. I once bought in London a Chinese toy, an imitation of a compound microscope, from which I took lenses so beautifully polished, as to be admired by one of the first opticians in London; and I have little doubt, that a clever workman in India could fashion lenses, with which a refracting telescope could be put together, quite as good as the best which Tully or Dolland ever made.

The above may appear a startling assertion, but no optician will deny the possibility of its being correct; for the fact is, that workmen are totally unable to give a particular required figure to a lens, and lenses of required focal distance for forming the achromatic object glasses of the best telescope, can only be procured by selecting the best among numerous failures, (whence the high price), and modern science has only improved these instruments, by teaching the proper theoretical principles upon which to compound their various parts.

In the above, it is by no means my intention to attempt to detract from the merit of the constructions of our best artists, but merely to shew, that the perfection of modern instruments is due more to the skill by which their parts are contrived and arranged, than to the mechanical skill by which the parts are executed.

It is generally imagined by Native workmen, and by many gentlemen in India, that with a pattern to copy it is easy to make any thing, this is, however, very far from correct; for unless shewn how to do it, it would be as impossible to construct the simplest philosophical instrument, as it would be to copy a telescope, or a chronometer, by the aid of a pattern only.

It is possible, besides, that the country may afford many advantages

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 electrical machines and grinding lenses, I am perfectly acquainted, from having 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 workshops 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 corrected, 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

Madras, had compiled notes for a similar purpose; his death having unfortunately prevented a revision of his first valuable, though crude, little publication, I have therefore made use of his able abstract of Rose's work, with such corrections and alterations as I considered necessary, and it has been necessary to rewrite nearly the whole.

It was not my intention ever, with my present experience, to have so soon undertaken the authorship of a compilation upon the subject; but having been applied to by the Rev. Mr. Garrett, of the Wesleyan Mission, for a work adapted for the Natives of this country, who might be anxious to acquire an elementary knowledge of chemical science, and finding that Dr. O'Shaughnessy's excellent little Manual was out of print, and there being no work printed in England, at all adapted for the perusal of Natives, I have determined on commencing at once the preparation of a work adapted for the purpose.

As the labour and time required for writing a complete work of this kind would be greater than my pursuits and official occupations would enable me to spare for the purpose, Mr. Garrett has agreed to share with me the labour of compilation, and he has therefore undertaken to draw up the part descriptive of the chemical elementary substances.

While so many excellent treatises upon the different branches of Chemistry exist, no originality can be expected in a work of this kind, and it must be therefore regarded, merely as a compilation of the information from other works, abstracted, condensed, and made as practical as possible.

In endeavouring to lead the Native student on to a general view of the useful application of Chemistry, it has not been forgotten, that the subject may combine with that brief and assorted information which renders the work a "Manual of Chemistry," which will be useful, as it is hoped, to those gentlemen in India, who possessing an elementary education upon the first principles of Chemistry, are yet deterred from the practical uses of the science, by the remembrance of the extensive and costly apparatus which they have seen used by their instructors in Europe.

The Native medical practitioner will find a knowledge of this science of the utmost value in assisting him in arriving at a knowledge of the composition of the various mineral productions which the country affords, so as to enable him to ascertain what may be useful to him,

and also enable him to prepare economically and independently of the manufacture in Europe, those chemical preparations which are found so valuable in European medical science. It will enable him to correct and to apprehend the absurdity of many incongruous preparations now ignorantly made use of by Native practitioners, and understand the effects of many which are very mischievous.

A knowledge of Chemistry will enable him to ascertain the quality and properties of the juice of plants, and the decoction of leaves and bark of trees, many of which have been found very valuable in Native practice, and which afford to the skilful chemist a cheap and economical substitute for the more costly chemical preparations employed by Europeans.

It will enable him to prescribe antidotes for the frequent attempts at murder, perpetrated but too often with impunity by poison, among the Native community, upon the slightest personal pique, or feeling of revenge or resentment; but which will receive a severe check from a certainty of detection and conviction, if persons competent to examine into the circumstances were at hand.

To the European amateur, extensive opportunities for the useful and gratifying practices of Chemistry present themselves, with investigations of the mineral resources of the country. In the investigations of the properties and composition of the juices of numerous plants and trees indigenous to this country, but which in Europe cannot be obtained, except in a state of partial decomposition; and the oriental chemist has thus laid open to him a vast field of research, in the pursuit of which he may find the highest gratification, and engross to himself opportunities, which the perhaps more generally skilful chemist of Europe may envy in vain.

If his ambition lead him to seek a higher field, and measure his skill against that of European proficients, there are numerous chemical compounds which have been as yet but imperfectly examined, and upon which his analytical researches may be most usefully employed; while the extensive leisure which many of the officers in the employ of the Government possess, the cheapness of fuel and labour, may enable any one, if he is diligent and enterprising, to seize upon some of those honors which distinguished scientific knowledge has ever received in all countries.

In Europe, where the works of authors are offered for sale, the public have a right to criticise their value, and manner in which the authors have executed their task. In the present case it is far different, the purpose of the work is above criticism, the execution beneath it. The expediency of an attempt to diffuse knowledge will be denied by none, and is indeed the object of the press from which it issues. The imperfections of the execution is a necessary consequence of the limits of the work, and will be attempted to be improved, should public opinion call for another, and more extensive, and of course more expensive edition.

The practical applications of chemical science for the purpose of trade and gain are very numerous.

Carbonate of Soda can be readily and cheaply made by simply crystallizing the solution obtained by lixivating the Soda Earth, (Chour Munnoc,) of the soils of many parts of South India.

Carbonate of Potash can be made by deflagrating Saltpetre with charcoal in an iron pot, (vide description of process under head of Potash from Cocoanut Leaves, Indigo Stocks, &c.)

Prussiate of Potash can be very readily made in India, as well as in England, and as it costs there 7d. a pound, and the material required, and the labour are very cheap in India, and the iron pot required easily procured from England, or may be even made in India, it may be made a profitable article of manufacture, (vide description of process of Manufacture.)

Acetic Acid may be made from the decomposition of Wood, (vide process), or by the decomposition of Alcohol by powdered Platina, as Dr. Ure informs us is actually and profitably employed in some parts of the Continent of Europe, where Alcohol is cheap, in converting it into vinegar; it of course can be still more profitably used in India, where Alcohol is still cheaper. Acetate of Soda might be manufactured for importation to England, for the purpose of decomposing it for the manufacture of Acetic Acid, in case the Excise Laws in England should cause a difficulty to the import of the Acetic Acid, or in case Sulphuric Acid cannot be procured at a sufficiently cheap rate in India.

Muriate of Morphia may be readily made in India, for 1-100th part the price in Europe, as Opium is sold in many parts of India at a very low price.