282 
i 
should have thought that Mr. Walkden’s letter, to- 
gether with my lengthy quotation from his book, 
would have been more than sufficient to remove any 
injustice that might have arisen through a statement 
of claim being made in the reviewer’s and not the 
author’s words. At the same time, it is necessary to 
warn readers that the amended claim contained in 
Mr. Walkden’s letter must be read in conjunction 
with the lengthy quotation in Narurr, or better with 
the contents of the book itself, otherwise a false idea 
may be formed of the author’s treatment. The only 
accelerations which the air can be said to impress 
on an aéroplane in the recognised Newtonian mean- 
ing of the term, are those due to the pressures of the 
air on its supporting surfaces, and are measured by 
the accelerations which the aéroplane would undergo 
if no other forces acted on it, their direction being in 
the direction of the corresponding impressed forces. 
In these circumstances a gust having a downward 
velocity would impress a downward, not an upward, 
acceleration on the aéroplane. It will be seen that 
the quotations from his book in my letter contain no 
reference to accelerations impressed by air pressures 
on the plane in this sense, and, while I am quite 
willing to accept the author’s amended statement of 
his claims, I should not feel justified in stating these 
claims in this form without his written authority.” 
Six years ago Prof. O. Knoblauch, of the Technical 
High School at Munich, determined the specific heat 
of superheated steam, at constant pressures, for tem- 
peratures up to 662° F., and pressures up to 124 |b. 
per sq. in. These experiments were conducted on a 
scale which directly appeals to the engineer, and the 
results, which Prof. Knoblauch obtained in con- 
junction with Dr. Max Jakob, are accepted largely 
by engineers. Engineering for November 7 contains 
an account, with drawings of the apparatus em- 
ployed, of further experiments by the same investi- 
gators. Knoblauch has extended the range to 
1020° F., up to pressures of 114 Ib. per sq. in., and 
the experiments are being continued at higher pressures 
up to twenty atmospheres. Jakob has attempted to 
check the results by calculating the specific volume 
of steam, for the same high range of pressures and 
temperatures, from the experiments of Knoblauch and 
his collaborators, and also from the deductions of 
H. N. Davis, and by comparing these volume results 
with those directly determined. The research shows 
that the specific volume can be calculated from the 
specific heat, and the experimental values for the 
specific heat are thus confirmed. The general result 
is that the specific heat of steam at constant pressure 
increases with pressure, especially near the saturation 
line, though much less so, and scarcely at all finally, 
as the degree of superheating is raised. As the tem- 
perature rises, the specific heat, c, decreases to a 
“minimum, to increase again slightly. 
Tue Cambridge University Press has recently made 
further additions to the ‘‘Cambridge Manuals of 
Science and Literature.’ The series now numbers 
eighty volumes, and its general excellence, to which 
attention has been directed on former occasions, 
well maintained by the half-dozen books which have 
NO. 2300, VOL. 92] 
reste 
NATURE 
just been received. Three of the new volumes deal 
with biological subjects. Prof. G. H, Carpenter tells 
“The Life-Story of Insects,’ and provides an outline 
sketch of the facts and meaning of insect transforme 
tions. Prof. W. J. Dakin, in his little book on 
“Pearls,” give a summary of the most important 
facts about pearls, pearl fishing, and pearl formation. 
The third biological topic is handled by Mr. H. 
Russell, who writes on ‘“‘The Flea,”’ and his book, 
which is, he thinks, the first in English devoted 
wholly to the subject, will prove particularly useful 
now that it is known that fleas are the active agents 
in spreading plague. Dr. E. J. Russell contributes — 
a book on ‘The Fertility of the Soil,” which is — 
addressed to all who are keenly interested in the — 
soil they are cultivating and want to know something 
more about it. Prof. A. H. Gibson, under the title, — 
“Natural Sources of Energy," discusses the problem — 
of forecasting the conditions of life and activity in — 
future centuries. The sixth book, on ‘‘The Peoples of — 
India,” is by Mr. J. D. Anderson, who gives a popular — 
account of the race and caste, the languages, and the 
religions of the various peoples in our Indian Empire. 
Mr. Recinatp Cory has received permission of the 
King to dedicate to his Majesty the volume, entitled — 
“The Horticultural Record,’ which is to be published — 
next month by Messrs. J. and A. Churchill. The 
work will contain numerous plates, coloured and half-_ 
tone, reproduced from photographs taken at the Royal ~ 
International Horticultural Exhibition, 1912. Several — 
well-known writers contribute articles on the progress _ 
of horticulture since the first international exhibition 4 
in 1866. 
Messrs. LoncMans, GREEN AND Co. have in pre- 
paration ‘“‘Chemistry of the Radio-Elements, Part ii., 
The Radio-Elements and the Periodic Law,” by Mr. 
Frederick Soddy, F.R.S. This is an extension of the 
original monograph, and covers recent generalisations — 
connecting the radio-active disintegration series with | rs 
Mendeléeff’s table. 
OUR ASTRONOMICAL COLUMN. 
ASTRONOMICAL OCCURRENCES FOR DECEMBER :— 
Dec. 1. 22h. 1m. Uranus in conjunction with the 
Moon (Uranus 3° 9’ N.). 
2. 3h. om. Mercury stationary. 
», 8h. 5m. Mercury in conjunction with 
Venus (Mercury 1° 34’ N.). 
6. 21h. om. Saturn at opposition to the Sun. 
10. 12h; om. Mercury at greatest elongation 
W. of the Sun. _t a 
12. 15h. 58m. Saturn in conjunction with the — 
Moon (Saturn 6° 45’ S.). 
15- gh. 57m. Mars in conjunction with the — 
Moon (Mars 0° 59' S.). 
peeten., 36m. Neptune i in conjunction with the 
Moon (Neptune 4° 29! S.). : 
20. gh. 44m. Variable star, Algol, at mini- — 
mum. 
21. 22h. 35m. Sun enters sign of Capricornus. 
Solstice. 
23. 6h. 33m. Variable star, Algol, at mini- 
mum. 
25. 20h. 23m. Mercury in conjunction with 
the Moon (Mercury 5° 26’ N.). 
