262 



APPKNDIX. 



25. Any vessel, filled with sand which has been heated over a fire, 

 with rods of different substances, nearly of an equal size and length, 

 and thrust with one end into the hot sand, in an inclined or nearly 

 horizontal position, will exhibit the various conducting powers of these 

 rods by melting pieces of wax or tallow placed on the ends most re- 

 mote from the sand. 



26. The expansion by heat may be demonstrated by fitting an iron 

 rod to a hole in sheet iron ; on heating the bar, it can not be made to 

 enter. Or, if a hot iron ring be slipped on a tapering cold iron rod, it 

 will contract on cooling so that the force of a man can not withdraw 

 the rod. 



27. The rising and descending currents in a vessel of heating water 

 are easily rendered visible by throwing into a glass vessel, or flask, 

 over a lamp, particles of sawdust from any hard green wood, whose 

 specific gravity is about the same as that of water. 



28. Instrument figured on p. 241, for showing the principle of the 

 steam-engine. 



29. Experiments in latent heat may be easily exliibited with the as- 

 sistance of a common thermometer. 



30. Tin mirrors for showing radiation, p. 254. 



Second List, containing a few of the more costly pieces of appara- 

 tus for experiments as described in this treatise. 



1. A good compound or solar microscope will exhibit the minute 

 animalcules described under the head o{ Divisibility. The larger of 

 these animalcules may be seen in old strong vinegar, and the smaller 

 in a drop of water taken from a vessel in which a portion of raw po- 

 tato has been soaked a few hours in a warm place. The same instru- 

 ment will show the pores of wood mentioned under the head Impene- 

 trability. 



2. Atwood's machine, p. 39. 



3. A good dynamometer for field experiments is of great value and 

 importance. 



4. An air-pump, with the several pieces of apparatus connected with 

 it, shows, in an interesting and striking manner, several important 

 principles. 



