and Miscellaneous Implements at Bristol. 119 
single-row machine, with an active horse, will top and tail from 
3 to 4 acres a day, effecting a saving in . 
expense of bs. to 6s. an acre at least, ^ig. 2b.— Elevation on 
This, if it works well, is a most practi- 
cal and important improvement, making 
the machine almost self-acting. Fig. 24, 
a plan of the saw frame, and Fig. 25, 
showing elevation of the slotted standard, 
through which the saw frames rise and 
fall, will illustrate the chief features of 
this improvement. 
Traction Engines. — Considerable im- 
provements have been recently made in 
Traction Engines, which tend to increase * 
their practical utility, by stronger con- 
struction and increased duty, especially / 
by the use of driving wheels of larger dia- j 
meter. Both Messrs. Aveling and Porter i_ 
and Messrs. Fowler and Co. exhibited 
engines with 7 feet wheels. A short description of the special 
features in each case will be read with interest. 
Messrs. Aveling and Porter s Engine, No. 72 in Catalogue, is 
described as an 8-horse power, road-locomotive, with Aveling's 
patent wrought-iron side-plate brackets. The peculiar and novel 
arrangement of gearing, which has been patented, will be best un- 
derstood by reference to the plan (Fig. 26, p. 120). From this it 
will be seen that all the gearing upon the crank-shaft and counter- 
shaft is contained within the side-plate brackets, by which the 
width of the engine is lessened by a foot, overhung gear dispensed 
with, and the fly-wheel brought close to the crank-shaft bearing. 
The chief object of this invention is to enable road-locomotives, 
of say 6-horse power and upwards, to be used on railways, the 
usual gauge of which is less than the gauge required for the road- 
wheels of engines of such capacity. The two pinions of equal 
size, marked a, are cast together and keyed fast to the crank- 
shaft, instead of sliding on feathers as formerly. The intermediate 
shaft, shown on the plan, is fixed, but carries a revolving sleeve, 
on which are keyed the wheels which transmit the motion to 
the wheels on the counter-shaft. On the left-hand end are two 
wheels of different sizes, to give fast or slow motion ; on the 
opposite end is the driving pinion, which is cast on the sleeve. 
The sleeve can be moved into three positions by a hand lever, 
and retained in each securely by a strong pin ; in this way the 
driving gear can be made slow or fast, or disconnected altogether. 
In the illustration, the gearing is shown in its fast speed posi- 
tion ; but if the sleeve is shifted to the right, the second pinion 
