THE STEAM TURBINE—PARSONS. 108 
and wheel, without the necessity of very high peripheral speeds of 
blades, such as are necessary with the single-wheel type. As regards, 
however, “ multiple series action,” the principle resembles the com- 
pound turbine. 
The expansion process in nozzles, and subsequent sinuous treat- 
ment of the steam, is repeated several times by four or more similar 
wheels on the same axis, but in separate steam-tight chambers, until 
the steam is fully expanded. 
If there are four such operations, the velocity of outflow from the 
nozzles will be about 2,000 feet per second, and the peripheral velocity 
of wheel about 400 feet per second; and at each operation the steam 
is expanded through one-fourth of the whole range, and at each it is 
brought to rest before flowing to the next chamber through the jets. 
A great many other varieties of the turbine have been proposed, 
and some have received a limited application. The Rateau, the Reid- 
ler Stumpf, the Zoelly, the Escher Wyss, and many others might be 
mentioned as varieties of the three fundamental turbines we have con- 
sidered ; indeed in some cases the variation would appear to have been 
only a retrograde step, and represents some discarded form tried by 
one of the originators of the three fundamental types. 
As far as we can gather from the history of the steam turbine, it 
may be said broadly that all the chief features at present in use in 
turbines have been suggested or described in the rough by experi- 
menters long ago in the hundred and more patents prior to 1880. 
For instance, Hero of Alexandria, B. C. 130, made a reaction 
wheel. 
William Gilmore’ first suggested the compound steam turbine in 
1837. 
Matthew Heath first enunciated the principle of the diverging 
conical jet in 1838. 
James Pilbrow in 1842 used cupped buckets, and suggested a sinu- 
ous treatment of the steam. 
Robert Wilson developed the compound steam turbine to a con- 
siderable extent in 1848. 
It would take too long to trace the initiation of each tdea, but 
we may say, in the light of recent experience, that most, if not all, 
the designs showed a want of knowledge of the properties of steam 
and materials, and could not have given a satisfactory performance. 
Let us again recur to the compound turbine, and look more closely 
into the principles of its working, and more particularly consider the 
course of the steam in its passage through the vanes or blades of the 
engine. 
Viewing the turbine as a whole we see that the steam passes through 
the forest of fixed and moving blades just as water flows from a lake 
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