SEPTEXBER, 1908. MON!l!HLY WEBTHER REVIEW. 286
The work of the station is carried on as follows:
Every day, before the flights are begun, the wind conditions
as high up as possible are determined, either from the move-
ment of the clouds or, preferably, by means of pilot balloons.
We thus decide whether we had better send up a kite or E
captive balloon; taking into account the fact that the boat
must be run as short a distance as practicable, in order to
economize coal. We also decide from what point on the lake
the flight should be begun so as to have as much room as
possible for the vessel to run in and not be obliged to aban-
don the flight prematurely on account of nearness to the shore.
During the summer months we have, as a rule, used captive
balloons of rubber-coated cotton or silk, and having a capac-
ity of 30 to 50 cubic meters. As they have a vertical ascen-
sional velocity of about 3 meters per second the ventilation thus
produced fully suffices to prevent the effects of solar radiation.
In many cases, however, a small electric ventilator is sent up
with the apparatus. I n winter we shall more often use kites
of the Marvin and Hargrave types, having 5 to 7 square meters
lifting surface. Our captive balloons have attained altitudes
as great as 4,000 meters, but with kites we have not yet gone
higher than about 3,000 meters.
The results of the ascents are promptly transcribed and
telegraphed to the meteorological central stations of southern
Germauy (Strassburg, Karlsruhe, Stuttgart, and Munich), the
Deutsche Seewarte at Hamburg, the Lindenberg aeronautical
observatory, and several of the Public Weather Service centers
in northern Germany. Our telegraphic reports have generally
been early enough to use in making the weather forecast issued
between 10 and 11 a. m.
The station owes its existence to the efforts of Professor
Hergesell, who as early as 1901, in collaboration with Count
Zeppelin, flew kites-without instruments, however-from a
small motor boat on this lake. The station was erected and
has been maintained by contributions from the Imperial Gov-
ernment and the governments of the four South German States,
Bavaria, Wiirttemberg, Baden, and Alsace-Lorraine. It is
located at Friedrichshafen, in Wiirttemberg, and is under
the administration of Wiirttemberg. The station building,
see fig. 2, which includes workshops and the necessary ofhes,
stands on the harbor front, close to the anchorage of the
kite-boat. The letter is of the torpedo-boat type, is 27 meters
long, 3.4 meters beam, and has an engine of about 350 horse-
power. The reel is
driven by an electric motor. The vessel was especially de-
signed for kite and balloon flights, was built in 1907 at the
Schichau yards, in Elbing, and cost 713,000 marks, or $18,000.
It is named Gnu-after one of the messengers of the gods in
the northern mythology.
THE REFLEC'I'INC3 POWER OF CLOUDS.
The following article is compiled from the note of May 27,
1908, recently distributed by Messrs. C. G. Abbott and F. E.
Fowle, jr., from the Smithsonian Astrophysical Observatory
at Washington, D. C.-C. A.
The diffused reflection and radiations from fog and cloud
and even dusty air, are of appreciable importance in dynamic
meteorology and even climatology. They are so analogous
to those from solid matt surfaces that the formulas given by
Abbott and Fowle must closely represent the natural intensity
when the incident light is homogeneous and the cloud parti-
cles are much larger than the incident wave lengths.
A perfect matt surface may be defined au one which reflects
diffusely the whole of the radiation incident upon it, in such
a manner that equal solid angles observed on such a surface
contribute equal amounts of reflected radiation, independent
of the nadir distance.
Let AB, in fig. 1, represent an infinitely extensive plane of
perfectly matt surface; let CD represent an infinitely extensive
It has a maximum speed of 19 knots.
plane parallel to the plane AB. Let a, 6, c, d, be four equal
arena situated so that ac is normal to AB and the angles dac
and bca are equal. Let them be represented by the symbol i.
Let the zenith distance of the sun be Zand let K be the amount
of radiation it sends to an area equal to a situated at right
angles to the solar beam. Then the amount of solar radia-
tion on a, or b, is KcosZ.
,J3 a A 6
FIG. '1.-Reflecting power of clouds.
By diffuse reflection the area u sends the uame amount of
radiation to the area d that b sends to c. A ring drawn in the
plane CD about c as a center, with a radius equal to cd would
contain as many areas equal to d as a similar ring drawn
about a as a center in the plane AB. For each such area
situated in the upper ring in a given position with regard to
a as a center in the plane AB. For each such area situated in
the upper ring in a given position with regard to a, there is
an area on the lower ring to which c bears exactly the same
relation of position. From this it follows that the sum of all
the radiation received by c is equal to the sum of all the radi-
ation diffusely reflected by a; and this, since the surface AB
is a perfect matt surface, is equal to the total amount of solar
which falls on a.
Let Q be the amount of diffusely reflected radiation which
a surface of the area c would receive if directed toward an
area of the surface AB subtending a solid angle equal to that
of the sun. Let u be the angular semidiameter of the sun.
Then the angular area of the sun is id.
For an element of angular area upon the plane AB at nadir
distance i and azimuth A the expression is sin i . di. d-4. Such
an element will reflect upon the horizontal area c the amount
of radiation
Q sin i. cos i. di. d d
ii 1.l-
Hence, the total reflection upon c! is
Hence,
0 ,lp = K cos z
and
Then, neglecting the difference in height above sea level be-
tween the cloud and the observer, every area of a perfectly
matt cloud subtending a solid angle equal to that of the sun,
would reflect to the measuring instrument an amount of radi-
ation upcosZ times the amount of radiation received directly
from the sun, provided both the direct and the reflected beams
were observed at normal incidence. On August 28, 1906, 2
was 0.0000206.
But an allowance must be made for the loss of intensity of
the beam in its course from the level of the observer to the
cloud and thence back to the level of the observer, and for
the considerable difference of level of the cloud of August 22,
0 = Ku2 cos z.
286 MON!L!HLY WEA!CHER REVIEW. ~EPTEMBEB, 1908
1906, and the observing station. I n fact this correction would
be large. While no accurate measurements were made, it is
thought that the difference of level on that date was about
1,600 feet. The air pressure corresponding to this difference
of level would be about 0.055 .of the barometric pressure above
Mount Wilson. According to the pyrheliometry of August
21 and 23, 1906, we may estimate the general atmospheric
transmission coeacient for August 22 as 0.90 for vertical trans-
mission thru all the air above Mount Wilson. Hence, for ver-
tical transmission thru the layer in question the transmission
may be estimated at (0.90)0-m=0.994.
For the very large angles of zenith distance 2, and nadir
distance i, the paths of the beam in this layer ought not to be
taken as simply proportional to (seo Z+ sec i), and we shall
rather use the air-mass values of Laplace as given by Radau
in his ccActinometrie,” altho these are also of doubtful appli-
cation in the present instance. Let us call the air-mass y(Z)+
y( i ), where e is a function to be taken from the above sources.
Then the values of reflection given for August 22, 1906, in
Table 26 of the Annals, are to be increased in the ratio
1
to allow for the d8erence of level. No correction of this
kind is thought necessary for the values of September 13,1906,
as the cloud was practically at the level of the observer.
An entirely new set of apparatus for measuring the reflect-
ing power of clouds is now in place at Mount Wilson, and we
hope to obtain a great many additional measurements there
this year. We therefore refrain from computing at present
a new value of cloud reflection and of the albedo of the earth
from the observations of 1906.
0 3 %~~
EARLY METEOROLOGY AT HaRVaRD UOLLEGE. 2.
In a recent article’ on the early history of meteorology at
Harvard College the writer mentioned the announcement of
lectures by Isaao Greenwood, the first Hollis Professor of
Mathematics and Natural Philosophy. While the strictly
meteorological subjects comprise but a small part of this
announcement, and therefore presumably of the lectures, it is
probably one of the oldest extant recorde of scientifio lectures
in this country and thus has considerable historical interest.
A few pertinent historical notes which the writer has been
able to gather follow the Syllabus.” The absenoe of a full
text of the lectures and of contemporaneous aocounts of them
renders a detailed study impossible.
A
Course of Philosophical Lectures,
with a great Variety of
Curious Experiments,
Illustrating and Conjirniing
Sir ISAAC NEWTON’S Laws
OF
MATTER AND MOTION.
By ISAAC GREENWOOD, A. M., CFC.
ARTICLE I.
By B. Id. VARNEY, Asaistant in Meteorology. Dated Camhr.dge, Mass., SeptemberlO, 1908.
Of the FUNDAMENTAL PRINCIPLES of MATTER
Where the essential Properties of Space and natural Bodies,
are shewn, in a great variety of Experiments: And the NEW-
TONIAN LAWS of Matter denionstrded.
I. Of the ESSENTIAL PBOPEBTIEE of Space and natural
Bodies.
1 See Monthly Weather Review, May, 1908, XXXVI, p. 140.
LECTURE I.
OF EXTENSION-The Manner of Conceiving and the real
Proof of a Vacuuin, by several curious Experiments-The
inconceivable Divikbility of the Parts of Matter, shewn in
natural and artijicial Instances, by a Sett of niicroscopicd
Observations, and prov’d by Dr. Nkiuwenlyt’s Experiinent of
the Divirrwir of Water, by the Blopile; on which P r i n ~p l e
the Operation of the celebrated Engine to raiae Water by
Fire, mill be explained in a very large C d t thereof.
Lecture 2. Of the SOLIDITY and POROSITY of natural Bodies
in many usgful Experinlent8 and critical Remarks; where
particular Notice will be taken of the Alterations they are
subject to by Heat and Cold, Dryness and Humidity, Weight
and Levily, in many curioiis Experiments. And of the
STRUCTURE and FORMS of natural Bodies,-their in-
ward Disposition,-exlernal Co,ifiguration, with a Variety of
Experinients relating to the Changes of their Fornis on
many Considerations.
Lecture 3. Of the Fundamental LAW; viz. GRAVITY or
GRAVITATION, (where all its Properties will be uery par-
ticularly illustrated and confirmed) together with the other
two General Laws; viz. the COHESION and REPULSION
existing between the niinute Parts of Matter, in a great
Variety of Ezperinients.
Lecture 4. Of the SPECIAL LAWS of MATTER; viz.
MAGNETISM and ELECTRICITY; where their surpris-
ing and most curious Phmnoniena are shewn in a Sett of
very useful and delaghtful Experiments of &e Invention.
ARTICLE IT.
Of the FUNDAMENTAL PRINCIPLES of MOTION.
I. The Prinoipals of MECHANICS.
Leoture 5. Explanations of necessary Terms, with many
Experiments relating to the Places of the mechannic Centers
of Bodies, their Velocitierr, Quantities of Matler, and Momenta
of Motion.-The Fundaniental Propositions relating there-
unto, proved on proper Machines- Experiments about the
,falling, sliding, and rolling of Natural Bodies, kc., very
curious; the Solution of several entertaining Problems,
relating to Animal Motion and Action; with a Conclusion
concerning the Explanation of the Motion of the Astro-
nomical Bodies on these Principles.
Lecture 6. A full Explanation with many Experinients, on
the Five 3fechanical Powers or Simple Machines; viz. the
several Kinds of Bdlances, Levers, Pullies, Wheels and Axka,
Wedges or Screws; of Compound Machinerr; and the Inven-
tion and Use of many ustfirl and curioics Engine8,
Lecture 7 . Of absolute and relative motion.
1. Law of Motion, viz. That all Bodies continue in the State
qf Motioii or Rest, un@uliby, in a right Line, except so much
as that State i s Chang’d by Forces imnpress’d; with many
Examples and Experiments; Of the great Use thereof in
the Motion ?f Bodies proceeding from single and Compound
hpiilses. Of the Phenomena of Diagonal Motion and
oblique Powers.
2. Law of Motion, viz. That the Change of llEotion is always
proportional to tlw nioving Force iinpresdd; and is alzuays
made in the right Line i l l which thai Force is impress’d. Of
the Plicenomena of Arcelerated and Retarded Jiotion.
Of Projectile Motions.
Lecture 8. Of oblique Descents; where all the curious Ex-
periments and Obseruatiows relating to Pendulunis and their
Uses, will be made. Of Circular and EUlpticd Motion, with
many EqwritnetJs. Dr. Desagulier’s celebrated Experi-
11. Of [he NEWTONIAN LAWS of MATTER.
IL Of the NEWTONIAN STATICS.
Sir ISAAC NEWTON’S