VALPARAISO, a large town and important seaport of Chile, is yearly rising into rank as one of the leading commercial depots on the Pacific shore of America. In 1809 only 9 vessels entered the harbour, in 1836 the number averaged 40 per month ; in 1819 the total number of foreign vessels that entered was 968. The customs revenue for 1819 was 2,022,577 dollars. There are large ship building yards, and extensive bonding houses. Many vessels engaged in the trade come to Valparaiso for provisions, whici may be put on board without their dropping at anchor. Valparaiso is the central depot fo: the produce of Chile. Large quantities o corn, and other articles of provisions, art shipped here for Callao, Panama, and . Sax Francisco. Besides wheat, the chief export: are—copper (of which 76,5151 quintals were shipped in 1819), gold, and silver ; tallow and hides ; timber, indigo, wool, sarsaparilla, fruits. &c. The imports are—foreign manufactured goods,, chocolate, tea, coffee, sugar, hardware, ate., &c. The British exports to Valparaiso exceed a million sterling annually. The French and American commerce with this port is also very important. The trade of Valparaiso has greatly increased since the discovery of gold in California. Steamers ply regularly to Callao and other Pacific ports. VALVE is the name given to any apparatus by which, in an hydraulic or pneumatic ma chine, the bore of a pipe or any orifice may be alternately covered and uncovered, in order in the one case to prevent, and in the other to permit, the passage of the fluid.
The ordinary pump-valve, frequently called a Clack, consists of a piece of leather rather larger than the bore or orifice. Circular plates of lead or brass are fastened to the upper and lower surfaces of the leather; and the valve thus formed is capable, from the flexibility of the leather, of turning, as on a hinge, at the place of its connection with the rim. After a
certain quantity of water has forced its way through the orifice, the valve, by its weight, falls, and closely covers the orifice, so that the water above is in great part prevented from returning.
Frequently a narrow bar of metal is made fast across a circular orifice in the direction of a diameter, and two semicircular valves of leather, each of which is covered above and below with a brass plate of the same form, turn upon the sides of the bar as upon hinges. This is called the Double-Clack, or the But teVly-Valve.
The conical or Spindle Valve is a metal body in the form of a frustum of a cone, the side of which makes an angle of 45 degrees with a diameter of the base, and its convex surface is ground so as to fit exactly the corresponding side of the orifice, It is usually employed as the safety-valve to the boiler of a steam engine. The frustum is lifted up vertically by the pressure of the steam, and when the steam has passed, it falls back by its weight.
The valve employed for the usual air pumps consists Merely of a slip of thin bladder tho roughly soaked in oil, its breadth being little more than is necessary to cover the orifice. When the pressure of the atmosphere is in part removed from the barrel, some of the air which is in the receiver forces its way, by its elasticity, through the orifice, and escapes at the sides of the valve. The valves of ma chines for condensing air are like those of a rarefying pump, but they are placed in con trary positions.