o . INTRODUCTION. 
14. For the purpose of ascertaining the names and 
characters of minerals, attention must be paid to their 
form, surface, lustre, fracture, or the appearance of their 
internal surface when broken ; structure, transparence^ 
streak, or the mark left when scratched by any hard 
body; stain, or trace left when rubbed upon paper; 
cohesion, whether solid, friable, or fluid: hardness, or the 
resistance which they oppose when scratched ; tenacity, 
or the resistance which they oppose to the stroke of a 
hammer , flexibility > or their property of bending without 
breaking ; feel, or the sensation communicated by their 
surfaces when handled; smell, taste, adherence to the 
tongue, sound, specific gravity, or weight in comparison 
with that of water ; colour and electricity. 
15. To ascertain the chemical properties of minerals, 
one of the most important instruments is the blow-pipe. 
This is a tube which terminates in a cavity as fine as a 
small wire, and through which the air is forced, and 
made to play upon the flame of a candle. The flame is 
thus concentrated, and directed against small particles of 
the mineral to be examined, which is placed upon a bit of 
charcoal in a spoon of platina or silver. The air is forced 
into the blow-pipe by the mouth of the person using it, 
or by bellows attached to it for that purpose. Under 
this operation we have an opportunity of trying the ac- 
tion of other bodies upon minerals at a very high tempera- 
ture; and the properties which these experiments bring 
into view enable us, in many cases, to ascertain, not only 
the nature, but even the component parts, of minerals. 
SIMPLE MINERAL SUBSTANCES. 
16. As a necessary introduction to the study of mi- 
nerals, it is requisite to describe, in a brief manner, such 
