CHEMISTRY. 



31 



2. All the metals are capable of combining with 

 oxygen. The knowledge of the number of oxides, 

 and of the proportion of oxygen which they contain, 

 is of great importance. The following Table exhi- 

 bits a list of these oxides, as far as known, of their 

 colours, and of the quantity of oxygen in each, com- 

 bined with 100 parts of metal 



Table of 

 the oxides. 



3. Of the simple combustibles, carbon has been 

 only united hitherto to two metals, namely iron and 

 nickel: hydrogen gas dissolves arsenic, zhc, and iron, 

 seemingly in the metallic state : phosphorus combines 

 with most of the metals hitherto tried ; but these 

 compounds have been applied to no useful purpose : 

 sulphur likewise combines with most metals ; the 

 sulphurets are often found native ; some of them are 

 prepared artificially, as paints : we do not knowthe 

 action of boracium on the metals. 



\. The action of the simple incombustible) on 

 metals is not striking. 



5, The combination! of the metals with each other, 



called alloys, are some of them, as those of zinc and Elements 

 tin, of great importance. The greater number of of 

 them have only been very superficially examined. 



Ihemistry. 



DIVISION II. 

 OF UNCONFINABI.E BODIES. 



THE uncon finable bodies cannot be examined di- Unconfm] 

 rectly ; because we have no method of retaining them j^ >le ***' 

 till we ascertain their properties. We can only draw 

 inferences respecting them, by seeing the changes pro*, 

 duced upon those bodies into which they enter, or 

 from which they separate. They are four in number, 

 namely, light, heal, electricity, and magnetism. But 

 the examination of the two last is not considered as 

 the province of chemistry. The two first will oc- 

 cupy our attention in the following Chapters. 



CHAP. I. 

 Of Light. 



EVERV person is acquainted with the light of the Light. 

 8un, and of burning bodies, and that it is by means 

 of light that bodies are rendered visible. 



Huygens considered light as a subtile fluid filling 

 space, and rendering bodies visible by the undulations 

 into which it is thrown. While Newton, and almost 

 all other philosophers, consider it as a subtile sub- 

 stance, constantly separating from luminous bodies, 

 moving in straight lines, and rendering bodies visible 

 by entering the eye. 



Light takes about 8 minutes in moving across half Motion of 

 the earth's orbit, which is a space exceeding 94> mil- light- 

 lions of miles ; of course its velocity is not much less 

 than 200,000 miles in a second: From this velocity, 

 joined to the imperceptible effect produced by the 

 impulse of the particles of light on other bodies, it is 

 obvious that its particles are inconceivably minute. 

 Hence the reason that they produce no perceptible 

 effect upon the most delicate balance. 



While a ray of light moves in the same medium, or Refraction. 

 when it passes perpendicularly from one medium to 

 another, it does not change its direction. But when 

 it passes obliquely from one medium to another, it 

 changes its direction, and is then said to be refracted. 

 When it passes from a rarer to a denser medium, it 

 is refracted toivards the perpendicular j when from a 

 denser to a rarer, it is refracted from the perpendi- 

 cular. In the same medium, the sines of the angles 

 of incidence and refraction have a constant ratio. 



When a ray of light strikes obliquely against a Reflection, 

 plane surface, even though transparent, instead of 

 passing through, it is bent back in a contrary direc- 

 tion. Just as would happen if an elastic ball were 

 made to strike obliquely against the ground. The 

 ray is then said to be reflected. The angle of reflec- 

 tion is always equal to the angle of incidence. 



When a ray of light passes within a certain dis- 

 tance of another body, it is bent toivards it; at a. 



The letter P in the second column signifies Peroxide. 



