PUL 



PUM 



PRUNING SHEARS. Shears in I 

 which one of the blades moves on a ! 

 pivot, which works in an oblong open- 

 ing instead of a circular one, by 

 which means a draw cut is produced 

 similar to that efiected by a knife, 

 instead of the crushing cut produced 

 by common shears, which fractures 

 the section lelt on the branch, and 

 renders it liable to become diseased, 

 or to decay, instead of being covered 

 over with fresh bark. Pruning shears \ 

 are particularly adapted for cutting 

 spiny or prickly shrubs, such as the 

 different species of thorns, gooseber- 

 ries, or roses. 



PRIJSSIG ACID. Hydrocyfinic 

 acid. See Cyanogen. It is distilled 

 from many flowers and seeds, which 

 owe their odour to it, as peaches, 

 cherries, apple seeds, SiC. 



P S E U D O. A common prefix, 

 meaning false. 



PTYALIS.M. Increased sali- 

 vation. 



PUBESCENT, PUBESCENCE. 

 Covered with soft hairs. 



P U C COON. American alkanet. 

 Balschia. canescens. A perennial-root- 

 ed plant of the borage tribe, the root 

 of winch yields a red pigment, with 

 which the Indians colour themselves. 



PUDDINGSTONE. A conglom- 

 erate. 



PUDDLING. Ramming clay with 

 sand and water until it is converted 

 into an impervious mortar. 



PUERPERAL. Relating to partu- 

 rition. 



PUFF-BALL. The genus Lycoper- \ 

 don yields numerous puff-balls. The 

 dust was at one time used to stop 

 bleeding from wounds, as a styptic. 



PUGGING. The stuff laid be- 

 tween floors to deaden sound. 



PUGIL. A pinch of any stuff. 



PULMONARIES. A kind of spi- 

 der. 



PULMONARY. Relating to the 

 lungs. 



PULQUE. The fermented juice 

 of the Mexican aloe {^Agave Amer- 

 icana). 



PULSE. Leguminous crops. 



PULVILLI. The hairs, or a mem- 

 brane, which covers the feet of some 



insects, enabling them to walk on the 

 ceiling of rooms against gravity. 



PIJMICE. Porous lava. It consists 

 of silica, 77-5 ; alumina, 175 ; potash 

 and soda, 30 ; oxide of iron. 1 75. 



PU.MICED FOOT. In farriery, a 

 wide-spread hoof, the sole of which is 

 flat with the ground. 



PUMP. This machine is of great 

 use on the farm for many purpo- 

 ses. The various forms may often 

 be employed for collecting or distrib- 

 uting fluids. " Though the forms un- 

 der which this useful engine is con- 

 structed, and the mode in which the 

 power is applied, may be modified in 

 an infinite number of ways, there are 

 only three which can be considered 

 as differing from each other in prin- 

 ciple. These are the sucking pump, 

 the forcing pump, and the hfting pump, 

 so called from the manner in which 

 they act. 



" The sucking pump, or common 

 household pump, is an apparatus of 

 which the principle and construction 

 will be evident from the annexed fig- 

 ure. A A is a pipe of any convenient 

 length, the lower end of Fig. l 

 which reaches below the 

 surface of the water in the 

 well or reservoir ; B is a bar- 

 rel, generally of greater di- 

 ameter than the pipe ; C a 

 valve opening upward ; D a 

 piston moved by the rod E : 

 in this piston there is also a 

 valve opening upward. When ^._— , 

 the piston is raised, the air "^CI 

 in the barrel between the valves is 

 expanded, and its tension, conse- 

 quently, diminished ; the pressure of 

 the air in the pipe, therefore, opens 

 the valve C, and the whole air in the 

 pipe and barrel becomes less dense. 

 In this state the atmospheric press- 

 ure on the surface, of the water caus- 

 es it to rise in the pipe, until the ten- ' 

 sion of the confined air becomes equal 

 I to the pressure of the atmosphere. 

 On again depressing the piston, the 

 ' valve in it opens, and the air passes 

 through it from the barrel as it de- 

 ! scends ; but the valve, C, is closed 

 by the downward pressure, and the 

 1 volume of water which has entered 



645 



E 



r 



f 



^ 



