Fuly 30, 1885 | 
NATURE 
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pinions roughed out in (3). Like (2) this is a simpler 
machine, but worthy of attention. The roughed-out 
pinions are here turned true upon their own centres. 
Notice that when the tool has turned off the necessary 
amount it stops of itself, till started for a fresh piece. 
(5) A pinion-polishing machine.—The polisher is driven 
to and fro by crank motion. After a sufficient number of 
rubs have been given the pinion turns automatically and 
presents a fresh face to the polisher, till all the leaves are 
done. The other side of the stand shows us a lathe 
requiring no special explanation. 
(6) An automatic machine for cutting pinions.—In this 
is exhibited an elegant arrangement for bringing a suc- 
cession of cutters into play. The principle, however, is 
very much better illustrated in the scape-wheel engine 
that follows ; we therefore defer explanation. 
Alongside of this machine is another for cutting the 
bevelled wheel teeth for keyless work. 
(7) A scape wheel tooth-cutting engine. The scape 
wheels to the number of sixty are threaded upon a kind 
of split spindle, which passes through the spaces around 
their arms, and holds them firmly. The spindle with the 
wheels around it looks like a solid rod of brass, and the 
cutter acts transversely so as to scoop a groove through 
all the sixty at once. Owing to the peculiar shape of 
tooth and the degree of finish necessary, seven different 
cutters are required. 
spindle being placed in position, the first cutter operates. 
When it has made one groove the spindle turns ; it makes 
another, and another, in all 15, which corresponds to the 
number of teeth. A sudden change now happens—the 
first cutter is diverted, and a second takes its place This 
cutter works through all the fifteen spaces, and then the 
next supersedes it, until all have had their turn and the 
wheel is finished. We understand that the whole sixty 
wheels are cut in about twenty minutes. 
(8) Another polishing machine, of somewhat similar 
design to (5). 
(9) Ona counter opposite to the main stand is shown 
an interesting instrument for determining the strength 
of watch-balance springs. In this the differential prin- 
ciple is employed, the spring to be tested being measured 
against one of known force, andthe number of degrees 
the latter is deflected registered. The springs are sorted 
into compartments corresponding to these numbers. 
There are two other tools not working at present, but 
still of considerable interest. The first is supplementary 
to (9), which only gives the strength of the spring within 
certain limits. ‘There is a normal balance with spring 
attached, and the balance and spring to be tested are 
mounted on an arm alongside of it. A lever sets both 
balances vibrating simultaneously, and it is easy to per- 
ceive in a few seconds whether their vibrations are syn- 
chronous or not. The other tool is automatic, and is for 
the purpose of drilling and tapping the screw-holes in 
compensation-balances. These holes are placed at 
irregular distances, as experience has suggested. By 
means of a divided plate the machine automatically finds 
these intervals. A very pretty feature will be noticed 
when the machine is drilling—viz. that the drill is with- 
drawn occasionally by the machine to free the cuttings, 
just as would be done by a workman. 
HENRY DENT GARDNER 
THE NICE FLOATING DOME 
WE have already (NATURE, vol. xxxii. p. 62) referred 
to the floating dome for the great equatorial 
of the Nice Observatory of M. Bischoffsheim. We 
give now an illustration from Za Nature, which shows 
the details of the annular floater. The entire dome is 
supported on the annular floater situated at its base. The 
floater, of hollow metal, swims in a circular caisson con- 
faining water holding saline matter in solution. When 
The actions are as follow :—The | 
the dome is in the position of normal buoyancy, the only 
friction which opposes its movement of rotation is the 
friction inside a liquid body, and consequently is extremely 
feeble, notwithstanding the great weight of the moving 
mass. Experiments prove that one man can easily set 
the dome in motion with his hand. The floater of the 
dome is open above like an undecked boat; it has 
a rectangular section of 1°50 m. in height by 095 m, in 
breadth. Its walls are bound together by rivets of steel. 
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The annular caisson, which receives the floater and the 
liquid, has a rectangular transverse section; its height is 
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1°50 m., and breadth 120m. The latter dimension thus 
exceeds the breadth of the floater by 0°25 m., which gives 
a lateral play of o'125 m. in the inside and 0125 m. at 
outside between the floater and the caisson. Finally, the 
caisson rests on thirty-six strong cast-iron supports, 
distributed at equal distances over the upper part of the 
mason-work of the tower. 
A NEW ENDOWMENT FOR RESEARCH 
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