xxii Agricultural Education — Examination Papers, 1887. 
8. Describe very briefly the preparation of metallic Iron from 
its ores. 
9. Give the chemical composition of the following : — Saltpetre ; 
Quartz ; Lampblack ; Chlorate of Potash ; Glauber's Salts ; Gra- 
phite ; Caustic Soda ; Zinc blende ; Bicarbonate of Potash ; Quick- 
silver. 
10. How is Sulphuretted Hydrogen prepared ? Give the prin- 
cipal tests for Sulphides. 
C. MECHANICS AND NATURAL PHILOSOPHY. 
November 9, 1887. 
[Three hours alloioed.) 
1. State what is meant by stable and unstable equilibrium. ' 
Give an example of a body in stable equilibrium and of a body in 
unstable equilibrium. ] 
2. Draw a right-angled triangle ABC, and suppose it capable | 
of moving freely in its own plane round D, which is a point in the 
hypotenuse A B such that A D is a fourth of A B ; the length of 
AC is 15 in., that of B C is 12 in. ; a force of 10 units acts from ; 
A to C ; find the force acting from B to C required to balance the ; 
former force. 
3. A B is a lever of the first order, 10 ft. long, capable of turn- j 
ing round a fulcrum (F) 9 ft. from A ; C D is a parallel lever of | 
the second order, 12 ft. long, capable of turning on a fulcrum at C, I 
and carrying a weight of 9,000 lbs. at E, 6 inches from C ; the ends i 
B and D are connected by a vertical link B D ; find the force P ' 
which, acting at A, would just support the Aveight at E ; find also | 
the tension of the link. | 
4. A thread is fastened firmly by one end to a fixed point A ; it ' 
passes over a smooth fixed point B, and carries a weight of 200 lbs. 
at the other end C ; given that A B is inclined downwards at an ' 
angle of 45° to the horizon, find (by construction or otherwise) the 
pressure on the point B. Wliat is tlie magnitude of the pull on the 
point A, and why ? 
5. What is meant when tlie velocity of a body is said to be 
uniformly accelerated 1 If the velocity of a body is uniformly 
I 
