vols. 4to. It rarely sells higher than from about ten to twelve shillings. It is often bound in three volumes.

"The History of Astronomy, with its application to Geography, History and Chronology, &c. by George Costard," 4to. 1767. In this is included an introduction to the use of the globes, but not systematically arranged. This work, like the last, may frequently be purchased at a very easy rate, and is deserving a place in the student's library.

In Practical Astronomy, we may mention as exceedingly useful to the young observer:

"An Introduction to Practical Astronomy; or the Use of the Quadrant and Equatorial, by George Adams.".

"A Treatise on Practical Astronomy, by Dr. Vince." This is a thin quarto; it contains a description of the several instruments in Practical Astronomy, and rules for computing and deducing the conclusions for which the observations are made.

For those young persons who would be conversant with the constellations, and principal fixed stars, and who have not access to a good celestial globe, we may recommend a little work, entitled

"Astrarium, or Principal Views of the Fixed Stars and Constellations, represented in twelve plates, one for each month in the year."

Having gone through the several departments of Natural Philosophy, and mentioned a few of the authors in which each branch of the science may be studied with advantage, by persons of different capacities and attainments in knowledge, it now remains to say a few words upon the subject more generally.

To books of science should, if possible, be added a course of experiments; it is an unfortunate circumstance, that the apparatus for demonstrating the facts in natural and experimental philosophy is necessarily very expensive; attempts have been made to invent a collection of instruments that should come within the reach of persons in moderate circumstances,

but without success. In schools, not exclusively devoted to classical literature, it is usual during each year, for the preceptor to go through a course of experimental philosophy, which cannot be without its use it excites the curiosity of young people, and may induce them hereafter to pursue science for its own sake, and furnish them with materials for thinking, and for spending their time in a rational and useful

manner.

It has been doubted whether experimental philosophy should be taught in the schools. If the genius of all children took the same direction, there would be no need of variety in their education; but as this is not the case, as their talents are as various as their dispositions, there seems no reason why different objects of pursuit should not be presented to them, thus leaving them, in some measure, to strike out for themselves their favourite studies. It has been asserted that the facts in natural philosophy could not be taught so readily as definitions in grammar, this has, however, been shewn to be erroneous; a work entitled "A Familiar Introduction to the Arts and Sciences," has been drawn up expressly with that view, divided into sections, containing about ten or twelve facts to be committed to memory; to which are added, where the subject requires it, illustrations, with references to plates, and questions adapted to the use of masters. These questions are placed in the exact order of the facts, but in examination they may be varied at the pleasure of the teacher. By the same author there are two other works adapted to young people, still farther advanced in the path of knowledge. These are "Scientific Dialogues," in six small volumes, which in the course of fourteen or fifteen years, have been very frequently reprinted, and have obtained a decided share of the public approbation: and "Letters on Natural Philosophy," in one vol. 12mo.

Of the same kind as the latter, but not embracing so many subjects, are "Lectures on Natural and Experimental Philosophy," in 2 vols. 12mo. by Dr. George Gregory.

"Elements of Science and Art, by Thomas Webster," in

two volumes, 8vo. is an excellent introduction to the several sciences on which they treat, including chemistry, and the application of mechanics, chemistry, &c. to a variety of elegant and useful arts.

In the second edition of "Enfield's Institutes of Natural Philosophy," introductions to chemistry, electricity, and magnetism, are added to the other departments of experimental philosophy, and the whole brought down to the time of the publication, in 1799: there is an advantage attaching to this, and to Martin's "Philosophia Britannica," which does not belong to those before mentioned, viz. the application of the elementary principles of mathematics to many of the cases that admit of it. The same may be said of Mr. Cavallo's "Elements of Natural and Experimental Philosophy," in 4 vols. 8vo. which is a book of real merit, but the style is not always simple and clear. Nicholson's "Introduction to Natural Philosophy," in two volumes, 8vo. may be recommended: as may, Adams's Lectures in five volumes. The later editions by Jones, are much superior to the original one by Mr. Adams.

"An Elementary Treatise on Natural Philosophy by M. R. J. Hauy," translated into the English by Dr. Olinthus Gregory, is not so well known as its merits deserve. It treats principally on the forces of bodies, Hydrostatics, Pneumatics, Electricity, Magnetism and Optics.

"Mathematical Elements of Natural Philosophy, &c. by James s'Gravesande, LL. D." translated from the Latin, by Dr. Desaguliers: and

"A Course of Experimental Philosophy, by Dr. Desaguliers," are very elaborate and excellent works, and were extremely popular during the greater part of the last century; they are still deserving a place in the libraries of the learned.

"A Course of Lectures on Natural Philosophy, and the Mechanical Arts, by Thomas Young, M. D." 2 vols. 4to. These lectures were originally delivered in the theatre of the Royal Institution, in which the author, instead of compiling from the elementary works then existing, resorted to the ori

ginal authors, and endeavoured to digest into one system every thing relating to the principles of the mechanical sciences, that could tend to the improvement of those arts, which are subservient to the conveniencies of life. Upon this plan the first volume is drawn up, and it includes all the branches of natural and experimental philosophy, with a very brief outline of natural history. The volume is divided into sixty lectures. Twenty on Mechanics and the Mechanical Arts: twenty on Hydrodynamics, and the same number on Physics. The plates, which are numerous, are referred to in the body of the work, but explained at the end of the volume: in many cases the explanations are much too brief for learners. Dr. Young's second volume contains: 1. The Mathematical Elements of Natural Philosophy. 2. A Systematic Catalogue of Works relating to Natural Philosophy and the Mechanical Arts, with references to particular passages, abstracts, and remarks. 3. Miscellaneous papers on subjects connected with the topics discussed in the volumes. Dr. Young's work is very valuable as a book of reference, but it will be found to be better adapted to the library of a philosopher and man of general reading, than to the uninitiated student.

In addition to the foregoing works, we may notice another class of authors, viz. those who give a syllabus, or outline, to be filled up by a person's own reading and researches: such is "A Plan of a Course of Lectures on the Principles of Natural Philosophy, by the Rev. Dr. Vince." This work was intended for the students of Cambridge, and was well adapted to recal to the mind all the facts and demonstrations detailed and exhibited in the public lectures.

On a larger and more useful scale, is a work very lately published by Mr. Playfair, entitled "Outlines on Natural Philosophy, being heads of lectures delivered in the University of Edinburgh." In these the author has given references to those works, in which his subjects are treated of at large.

CHAP. VI.

CHEMISTRY.

Importance of Chemistry to the Arts and Manufactures--Divisions of Chemistry. Simple Substances. Light-Caloric-Oxygen-Sulphur

Phosphorus-Carbon-Hydrogen-Metals-Earths-Alkalies-Acids.

THE object of Chemistry is to ascertain the ingredients of which bodies are composed, to examine the compounds formed by the combination of these ingredients, and to investigate the nature of the power which occasions these combinations. As an art, Chemistry is connected with the most important branches of the manufactures, and in proportion to the progress made in chemistry, a higher degree of perfection may be looked for, in the several processes which are necessary to the conveniencies and elegancies of life. The glass and porcelain manufacturers, the workers in metals, the dyer and bleacher, the tanner and soap-boiler, with many others, depend on chemistry for improvement in their several arts. As a science, it is connected with almost all the phenomena of nature; with the causes of rain, snow, and earthquakes:--with the production, growth, and maturity of the vegetable world:-and with the functions of animals; exhibiting the manner by which the food, taken into the stomach, is