OF THE PROPERTIES OF MATTER. 7 



ways owing to the pressure ot the air upon the water in LECT 

 the basin ; for as the tube is open at top, it is full of air ^x-v-%. 

 above the water, which will press as much upon the 

 water in the tube as the neighbouring air does upon any 

 column of an equal diameter in the basin. Besides, if 

 the same experiment be made in an exhausted receiver 

 of the air-pump, there will be found no difference. 5 



2. A piece of loaf-sugar will draw up a fluid, and a 

 sponge will draw in water : and on the same principle 

 sap ascends in trees. 



3. If two drops of quicksilver be placed near each 

 other, they will run together and become one large drop. 1 



4. If two pieces of lead be scraped clean, and pressed 

 together with a twist, they will attract each other so 



the column of water depends principally on the internal diameter of 

 the tube. Glass canes, admirably adapted for the illustration of this 

 fact, may be procured at the glass-houses for a few pence, and as they 

 are seldom drawn of one size throughout, a single cane may be divid- 

 ed into short lengths for the purpose. A very beautiful mathematical 

 figure may also be formed, by connecting two plates of flat glass in 

 such a way as to represent the two covers of a book partly opened ; 

 the edges being accurately in contact at the one side, whilst the op- 

 posite side of the plates are held asunder by a thin wedge. The 

 plates thus united, should be placed erect in a shallow trough of colour- 

 ed water, and in a few moments a curved line will be formed called 

 an hyperbola. It may be proper to state, that the figure is more im- 

 mediately formed, if an essential oil is substituted for the coloured 

 water. 



Note 5. The ascent of fluids in capillary tubes, has been applied 

 to the construction of a common filter, and the advantage it possesses 

 over a downward filter, arises from the facility with which the sediment 

 may be separated from the clear fluid, which in the ordinary mode of 



filtration tends to choke the apparatus. 



^ 



y<ite 6. A reference to the same cause will readily account for the 

 spherical form assumed by drops of falling rain, as well as a variety 

 of other meteorological phenomena : a popular poet has very beau- 

 tifully remarked, that 



"That very law which moulds a tear, 



And bids it trickle from its source. 

 That law preserves the earth a sphere, 



And guides the placets in their coarse." 



