Page:Popular Science Monthly Volume 88.djvu/728

 Making a Life-Saver of a Leak

��WHEN a heavy sea is running, one of the glass-covered portholes in the bow of a steamer is often crushed in — an accident which, while seemingly unimportant, has resulted in the foundering of many a ship. Water rushes into the opening at the rate of many gallons a minute. Should the

���The water tank covers a hole in the ship's side. Part of the interior is shown so that the balancing-chamber can be seen. The small tube at the top leads to the mercury gage which tells whether the ship is listing or not

��crew be occupied in other parts of the ship in clearing decks or battening down hatches, the broken port is likely to escape notice until enough water has entered to make the situation really serious.

An automatic registering device with a dial in the chart room or captain's cabin has been installed on several freighters, to indicate within a fraction of an inch exactly how much water the vessel is drawing both forward and aft. The instrument has been applied to other uses, such as measuring the depth of rivers and the amount of oil and other liquids in tanks aboard ship and ashore. In all of these applications the principle of the device is the same.

The natural law which governs the operation of the "pneumercator," as the invention is called, is nearly as old as mechanics. Simply expressed, it is that the weight of liquids having the same cross-section is directly proportional to the depth.

Described in a few words, the device consists of a pressure-gage, which regis- ters the weight of liquids in which it is sunk, and by means of a tube containing air indicates the pressure on a wall- gage. The apparatus is made up of three essential parts: a balancing- chamber, an indicator and a small pressure-pump. The balancing-chamber is connected by copper pipe line with the indicator, and the indicator is connected with the pump by means of another pipe line.

���A cargo steamer equipped with two pneumercators. The balancing-chambers are contained in the tanks which are indicated in the bow and stem. Holes in the ship's side, which allow the tanks to be filled, are placed a few inches below water line when the ship is unloaded.

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