VERTICAL ENGINES DRIVING DYNAMOS BY BELT ON ONE BED-PLATE.

The above being extremely compact, the belt must necessarily be very short, and a little more space in the direction of its length is advisable if possible, such as shown by another set of sizes, driven at more moderate speeds, as follows:

VERTICAL ENGINES, MODERATE SPEED, DRIVING DYNAMOS BY BELT ON ONE BED-PLATE.

A table of sizes and powers of these small engines under various speeds and pressures, which follows, will be found useful for reference and decision in this connection :

TABLE OF EFFECTIVE POWERS OF VERTICAL HIGH-SPEED ENGINES AT VARYING STEAM-PRESSURES

AND SPEEDS.

Most Economical Loads.-The above table appears to be sufficiently comprehensive for all powers up to nearly 90 effective horse-power, but it is usefully supplemented by a table drawing a comparison between these maximum effective powers and the most economical load, which is a point frequently lost sight of:

Any of these single engines may be coupled to another of same size, preferably with cranks set at right angles to one another, and will then give off an increased power, equal to nearly double the power of the single engine.

Such double engines are supplied in the same sizes as single engines, and are largely used for driving dynamos direct in ship-work of a high class.

They cost somewhat more than the bare price of two single machines.

A particular advantage of a double engine over a single is some gain in regularity of turning. There is practically no other economy, and thus, when the cost of a double engine comes to be considered, it is open to question if the

amount of extra cost needed to make it of compounding proportions should not be incurred.

Such small high-speed compound engines are made in infinite varieties of sizes to suit the exact conditions of their work.

COST OF DOUBLE CYLINDER VERTICAL ENGINES.

They are made for marine work, as launch engines, with shorter strokes than the above, and are then suited for coupling direct to dynamos, fans, and centrifugal pumps, as follows:

DOUBLE-CYLINDER VERTICAL ENGINES-SHORT STROKE AND HIGH

For the purpose of comparison, the following may be

useful:

HIGH-SPEED DOUBLE-COMPOUND NON-CONDENSING ENGINES.

This brings us to the point of considering what may be regarded as the developed vertical engine, viz.:

The Double-Compound Vertical or "Marine Pattern" Engine. The title "marine engine" is getting to be somewhat misleading, as the use of these engines is very extensive on land, where for a number of purposes they prove particularly suitable.

Wherever reversing has to be part of the engine's duties they are specially desirable, and, naturally, also where space is an object. The double and triple compound engine has shown its superior economy over the single cylinder, even apart from the process of condensing, which may or may not be adopted with either of them.

In no duty has the double-compound engine made more strides than in electric-power supply, where its short stroke, solidity, and balance of parts, and consequent ability to run regularly at a high rate of speed, make it easy to connect direct to the dynamo shaft or to drive the latter by one directly-connected belt.