NOVEMBER 20, 1913] 
NATURE 343 
the models experimented on, there is no special 
type which can be said to be the most advantage- 
ous from the aeroplane constructor’s point of view, 
and the choice of the most advantageous depends 
upon the conditions of the particular problem in 
each case. In the case of wings with reverse 
curvature it was found that the reaction was no 
longer proportional to the square of the velocities. 
The wings tested had sections similar to those 
_ employed by the principal designers of aeroplanes. 
electric motor in the wind tunnel; thus the results 
obtained more closely conform to the conditions of 
flight, and the “dynamic ” instead of the ‘“‘static”’ 
thrust is obtained. The conclusions to be drawn 
from the experiments are that the reaction upon a 
propeller cannot be assumed exactly proportional 
to the square of the relative velocity, and from a 
study of the model it is possible to predict all the 
elements of propeller action provided that the 
model be tested with the same relative velocity, 
_ both in magnitude and direction, that the full-sized 
_ propeller is expected-to use. This requires for the 
same velocity of translation a speed of rotation 
‘inversely proportional to the diameters of model 
and propeller. The distortion of the propeller at 
high velocities is mentioned as a cause of some 
variations observed in the results. Velocities of 
5 to 18 metres per second were used, and the pro- 
_pellers were driven at speeds from 400 to 1600 
revolutions per minute. 
By such experiments facts are being brought to 
light which already have had a great influence on 
aeroplane construction in France, and the expeti- 
™ments on models offer a safe guide to the be- 
haviour of the air upon aeroplane wings by the use 
of appropriate constants. From the results of the 
experiments the minimum effective power that can 
_ sustain flight is obtained for a given wing section. 
Thus a Blériot machine with a supporting area of 
25 Sq. metres, weight in service with pilot 588 kg., 
and an angle of attack of 9°, was found by the 
model to require a minimum effective power of 
24h.p. This, it is stated, is practically the power 
used. The effect of superposed planes is also 
| Studied; also the effect of aspect ratio upon the 
"reaction. In this connection it may be mentioned 
that the author first observed the curious varia- 
‘tions for a square plate with the Eiffel Tower 
dropping apparatus. The reaction on a square 
plate inclined 37° is nearly one and one-half times 
Reps.) Bs 
results on the eighteen types of wing which formed | 
| 
| 
| 
| 
| portion of the book. 
| is certainly very striking. 
| where. 
| souterrains.” 
| structures. 
| tions of some fairy souterrains give the work 
| point is marked, that of Knockdhu (p. 30). 
OUR BOOKSHELF 
Ulster Folklore. By Elizabeth Andtews 
xilit+ 121+xii plates. (London: 
1913.) Price 5s. net. 
Tuts dainty volume is made up of a collection 
of papers communicated to various societies 
and journals. As much of the information was 
collected at first hand, the book is a valuable 
contribution to the literature of Irish folklore. 
The expressed purpose kept in view was to find, 
and show, some correspondence between the 
description of Irish fairies and that of actual 
Pp. 
Elliot Stock, 
Propellers were tested by driving them by an | pigmies found, dead and alive, in various parts 
| of the world, and that purpose gives unity to the 
which is more of a monograph than a 
The correspondence made out 
There are also rare 
pigmies to be met with in Ireland as well as else- 
But of the actual existence of pigmy 
communities in Ireland no evidence is given. The 
fairies there, as elsewhere, haunt “raths and 
They occupy Neolithic megalithic 
The photographs, plans, and descrip- 
work, 
folklore drag-net. 
recognises the invariably 
Only on one plan the north 
If 
the true north is given, the cove, which is 87 ft. 
long, is oriented 70° N.W.-S.E. The entrance 
is south-east; and assuming a sky-line elevation 
of one degree, the star Antares is indicated about 
1700 B.C., a date by no means late for a Neo- 
lithic culture in the north of Ireland. 
There is some evidence to show “that Palzo- 
special value. One 
oriented creepway. 
| lithic man lived and worked in Ireland” (pp. 99- 
too). ‘‘Itis difficult to exterminate a people, and 
they could not be driven further west” (p. 104). 
One may add that the pigmy of folklore is much 
more ancient than the Irish Neolithic men. In 
the case of Ireland, however, what may be said 
with tolerable certainty is that the fairies are the 
Neolithic builders, and the case is well stated in 
a quoted statement of the late Mr. John Gray. 
“The stature of these primitive Danes and Pechts 
is five feet three inches, and they must have 
looked very small men to the later Teutonic in- 
| vaders of an av erage stature of five feet eight 
and a half inches” (p. 102). The souterrains of 
Ardtole and Maghera are 5 ft. 3 in. high. 
Joun GRIFFITH. 
Chemistry: Inorganic and Organic, with Experi- 
ments. By C. L. Bloxam. Tenth edition, Re- 
written and Revised by A. G. Bloxam and 
Dr. S. J. Lewis. Pp. xii+878. (London. 
J. and A. Churchill, 1913.) Price 21s. net. 
THE first edition of this well-known treatise ap- 
peared in 1867, and consisted of 630 pages which, 
as the preface of the present issue points out, 
sufficed to give a fuller account of the science 
of chemistry than the tenth edition can pretend 
to offer. The development of physical chemistry 
has rendered necessary a recasting of the first 
The periodic classification 
