MAY, 1897. MONTHLY WEATHER REVIEW. 207
search light which renders them visible is an invaluablt
assistant. A year ago some accounta were published relativt
to the cloud effects on Mount Low and Pasadena. According
to these accounts Mount Low is about 15 miles north-north.
east from Loa Angeles and about 6 miles in a straight lint
from Paradena. When the beam of light fell upon the bodiei of clouds they at once became luminous, so that all the de. taile of motion were visible; when the beam fell upon tht
falling rain the great cone of light glowed like molten metal
Distant clouds moving up the canyons were searched out and
made to glow as if in the midday sunshine. It seems as ii the formation and motion of fog and cloud at nighttimt
conld be advantageously studied by means of the search
light. The height a t which fog first forms, and its gradual extension upward and downward during the night, would be
a vmy interesting and profitable inveatigation.
WATERSFOUTS OFF LONG ISLAND.
On April 9 when the schooner George M. Grmt was within
B few knots of Montauk Point, the sea, which had been heavy
all along the Long Island coast from Fire Island, rapidly be.
came the roughest that Captain Pelton had ever seen. It Waf
about eight bells, or 4 p. m., and thick weather had prevailed all day. During a temporary lift in the clouds Captain Pel-
ton and his crew saw ahead four immense waterspouts. Three
of them were a t a comfortahledistance, but the fourth passed
by to starboard not an eighth of a mile from the schooner, Captain Pelton says that the noise made by the spout as it
whirled by the vessel was like that made by an immense corn-
sheller.
WATERSPOUT, ULOUDBURST, OR TOWADO.
These three terms are often used indiscriminately when it
would be easy to make a clear distinction between them. The
Cleveland World of April 1 reports that “ a waterspout on
March 31 at Pam, Ill., threw a train of five cars and engine from the track of the Illinois Central.” It does not appear
likely that the damage here mentioned was done by wind ; we
may, therefore, infer that we have not to do with a tornado.
A waterspout a t sea is, according to all established usages in
the English language, a different phenomenon from a heavy
rain. Rain often accompanies a waterspout, but is not the
prominent and characteristic feature. In the present case there could have been no waterspout properly speaking be- cause the phenomenon occurred over the dry land of the in-
terior of the continent. The daily weather map shows that the conditions were favorable for the formation of aevere
rains, thunderstorms, cloudbursts, and possibly tornadoes over Illinois on the afternoon of March 31 ; in fact a tornado was
reported in Arkansas, but not waterspouta properly so-called.
The use of the word “ waterspout,” when the writer really
means onlya heavy rain and wind, is not to bo recommended.
Such rains and winds are characteristic of thuiiderstorms and so-called “ cloudbursts.” I n the present caae it is likely that
rain did not alone do the damage that is reported ; a flooded
track and a strong current of water would be needed to throw an engine from the track, or possibly the flood caused by the
rain had undermined the track and thus indirectly caused
the derailment. In general, in such caaes as this it would be
more proper to omit the words “ waterspout ” and ‘‘ cloud- bhrst.” If the train was thrown from the track, or lifted
from the track, as the headlines of the above article had it, this must have been due to a severe storm, but certainly not
to a “waterspout properly so called.
CHaRaCTER OF THE SKYLIGm.
It is generally recognized that the influence of the sun-
light and diffused skylight on the assimilation and growth of
plank is brought about, first, by the heat that warms the
earth and promotes the rise of the sap and, second, by the
chemical action that is brought about by certain portions of
the solar spectrum or more properly by radiations of specific
wave lengths which fall upon the leaves of the planta and
determine the formation of chlorophyll. When planta are cultivated under tho influence of artificial lights, or in por- tions of the earth where the sunlight is obscured by cloud
and fog: their development is usually slower, and they often-
times fail altogether to produce a satisfactory sap or crop, or
mature seed. This failure is reasonably attributed to the nature of the light arid especially to the relative abundance
of the radiations that produce favorable chemical clianges as
compared with those that produce undesirable changes. Any investigation into the influence of climate on plants and crops and any effort to cultivate plants by artificial light
must take into account the relative energies transmitted in
different portions of the spectrum. This distribution of
energy with wave length is extremely irregular when the flame is produced by burning simple substaiices, as is shown
by the fact that the spectrum is generally a aeries of alter-
nating bright and dark or warm and cold spaces, but is much
more regular when the radiation emanates from incandeacent masses of solids before they evaporate into the gaseous con-
dition. The distribution of energy throughout the spectrum is also greatly affected by the reflection from any surface;
especially is this true in the case of the blue light of the sky,
which is apparently a species of selective reflection from the
minutest particles of aqueous vapor and which, notwithstand- ing ita visual feebleness, is yet a matter of the greatest impor-
tance to agriculture. The total amount of eneqgy received
by any plant from the whole vault of the blue sky will in
hazy weather equal that received directly from the sun and in the case of a thin layer of cloud or fog when the sun is in-
visible and the direct radiation therefore zero, the indirect diffused radiation may still be a large quantity. This latter
consideration suffices to explain why many planta flourish
in a foggy and cloudy climate and in shady places where the
direct sunlight never penetrates. The total energy involved in the molecular vibrations that
constitute radiation is not shown by its effect in producing
light or heat or chemical actions; these are but some of the modes in which a portion of that energy becomes appreciable
to us. This radiant energy is conveyed from point to point by the mediation of the ether, and the ether can only be-
some appreciated by its action on the so-called ponderable
matter. It is probable that the energy involved in the move- menta of the ether is far greater than that which is made
measurable by its visual, chemical, or thormsl results, for
there are still other results acconiplished by it, as shown by the phenomena of electricity, magnetism, and gravitation.
The following table is quoted from a paper in the Aiiaalen
ier P h y d m d Chemie, Vol. LIII, by Koettgen, who has meas-
ired the relative intensity of the light in the different parts If the spectrum from a large variciy of lamps and burning
iubstances. Her measures of tho sunlight and skylight par-
Jcularly interest the ineteorologist and agriculturist. They
were made in the first half of August, 1893, near Berlin, Ger- nany, in latitude N. 52O. At this seaaon and place the maxi-
num midday altitude of the sun varies from 5 6 O on August 1
KJ 62O on Auguat 15. The measurements were made by di- wcting the vision toward the blue skylight at a considerable
rltitude above the horizon, and probably in the northern por- ,ion of the sky, although that ia not specifically stated. The mesults are given in the first column. When directed toward
m overcast sky covered by an apparently uniform thickness
)f cloud, the measurements given in the fourth column were
Ibtained, and when directed toward the shining white side of
b cumulus cloud, thoae in the fifth column. When directed
award the sun itaelf, the measurementa giveu in the sixth
tnd seventh columns were obtained. The figures given in
208 MONTHLY WEATHER REVIEW. MAY, 1897
Wave length.
Y i m . 690 m 660
(1110
610 690 570 5lnl SXl 610 490 470
460 480
these columns express the relative ability of different sourca
of light to produce light of a specific wave length ; thus, foi instance, if a Heffner lamp, which was used by Miss Koettgen
as the standard, should a t the yellow wave length 590, givc
the same intensity as the blue sky, then a t the wave length
430, the blue sky would give a violet light that is 61.63 timea
as intense as the violet light of the Heffner lamp at that poinl
of the spectrum. The author used the spectrum photometel
invented by Dr. Arthur Koenig, and the table expresses visua:
results, and may not apply strictly to chemical or therma:
results.
Spectrum color.
-___
Red. orange.. orange. Yellow. Yellow. Yellow. Yellow. Ollve. Qreen. Green. Blue. Blue. Blue. Violet.
Blue sky light.
0.81 0. a, 0.40 0. a 0.74 1.00 1 .1 8 .P 8.49
6.75 9.41 18.17 88.96 61.68
Direct emlight.
I sky. I I
0. I 0.88 0.48
0. M 0.76 1.00 1.67
3.94 8.89
4.88 7.89
91. M 86. B
ia.84
0.81 0.46
0.69
0.88 1.00
8.14 3. I 4.80 6.66 11.87 19.86 80.78
0. m
1.1
0.81 0. w
’ 0.46 0.80
0.79 1.00 1.84 1.81
8.68 6.66
19.18
8. m
. 8.66
I...
.....
0. 80 0.89 0.48
0.62 0.80 1.00 1.84 1.86 8.1 8.68 6.48
8. 79
19.74 18. 80
ATMOSP-C VBPOR.
The relation between the air and the moisture that it con-
tains is very frequently stated incorrectly in elementary text books on physics and in ordinary popular explanatione
of meteorological phenomena. The error consists essentially in the idea attached to absorption, as in the sentence “a
cubic foot of free air at a temperature of 50° will absorb 4.28
grains of aqueous vapor.” This reads as though the writer
considered the air in the same light as a sponge. Now, a
sponge absorbs water by virtue of its own structure, and if the sponge were not in place the water would not leave ita
former position in order to ascend into the sponge. It is not
so with air. The vapor of water ascends into the air by
virtue of certain inherent properties of its own to which the
air offers a slight resistance; if the air were absent from a
cubic foot. of space the vapor would still fill that space. The above quotation should, therefore, read as follows : A cubic
foot of SPWQ, if saturated at a temperature of 50°, will con-
tain 4.28 grains of aqueous vapor.
It takes a little time for aqueous vapor to diffuse into and
thoroughly saturate a given cubic foot of space. It takes a
little more time if that space already has air in it, but when
the space is finally saturated the amount of the vapor is, so
far as can be measured, appreciably the same, no matter whether the air is present or not. We must, therefore, speak
of the vapor and the air as coexisting side by side, and it is
no more proper to speak of the air as having absorbed the
vapor than to speak of the vapor as having absorbed the air.
Owing to the mutual resistance of the air and vapor the
molecules of the one do not pass through and among those of the other as freely as they pass through empty space. This gives rise to what is called the coefficient of diffusion
or the time required for a unit-volume of either gas to com-
pletely interpenetrate a unit volume of the other. The time
required for this mutual interpenetration is also, of course, the time required for the mutual separation after they have
been mixed together. As this time is quite appreciable it follows that both the air and the vapor move along together either horizontally, as wind, or vertically, as iu the ascend-
ing currents that make clouds. Of course, in such a mixture
the temperature of the air and the vapor are precisely ‘the
same, and we can not warm or cool one without warming or
cooling the other.
If by any process the temperature is lowered below the
saturating temperature of 50° F. then the cubic foot of space can not contain so much as 4.28 grains of aqueous vapor and
the difference, whatever i t may be, must be condensed into
particles of water, forming haze, fog, clouds, rain, etc. The cooling just referred to is often brought about by the mere act of expansion as the warm moist air rises in the atmos-
phere. This expansion implies that work has been done in
the interior of the mixture of air and vapor. A mass of per-
fectly dry air or a mass of perfectly pure vapor would cool by expanding just as tho mixture does, but at ordinary temp-
eratures the cooling of the dry air will not convert i t into
liquid air, whereas the cooling of aqueous vapor can easily convert it into liquid water. We have seen it stated that
when the air expands i t is, in this rarefied condition, not able
to absorb so much aqueous vapor as in ita former unexpended
or denser condition. But this is a mistake. Rarefied air at ordinary temperatures in the laboratory will hold as much
vapor as denser air at the same temperature. The reason
why rarefied air on mountain tops does not ordinarily contain
as much vapor as the denser air at the base of the mountain is that the mountain air is cooler; it ie the temperature and
not the pressure that regulates the quantity of moisture in
the upper strata of the atmosphere.
THE llbETE1ORO~IOAL USE OF THE TERM “LOOAL.”
The adjective “local” in the expressions “local rain,”
“ local storm,” “ local wind,” “ local frost,” etc., seems to re-
quire some special definition, so that the word may be used
in a fairly uniform seuse by all meteorologists. As prelimi- nary to any attempt at a definition it will be best to collect
together a few examples illustrating the wide range of ordi-
uary usage.
The storm of September 6, 1895, in Oklahoma County,
Okla., is stated in the Bulletin of the State Weather 8ervice for that month to have been “ the heaviest rainfall and thun-
derstorm of the season ; it was purely local in nature and ex- tended only over an area of 300 square miles.”
A very heavy rain in southeastern Indiana is said to have
given rise to “ local floods ” and destruction of crops over a
region about 7 miles in diameter.
A series of “ local rains ” on the southern coast of Florida covered a region parallel to the coast for 60 miles north and
south, and from 1 to 6 miles broad east and west.
A tornado is a “local phenomenon” whose destructive winds are felt at irregular intervals over a region that may,
in an extreme case, be a 100 miles long and 1 mile wide, but
is more apt to be from 6 to 20 miles long and scarcely & of a
mile wide. A “ local cloudburst ” may occur in a mountain valley and
3ver an area of scarcely 4 of a square mile.
Is it possible to attach any definite idea to the term local?
Judging from the preceding usages a West India hurricane
begins as a “ local whirl ” in mid-Atlantic, grows into an ex-
tensive disturbance over the West Indies and our Atlantic :oast, becomes a general storm in the North Atlantic, and dis-
zppears by merging into the “general circulation of the Northern Hemisphere.”
The terms local and general are necessarily indefinite, and
ire needed for use with that understanding. But in order to give precision to our observations, it is hoped that observers will, when practicable, specify approximately the area in
quare miles over which any phenomenon is visible rather
&an content themselves with an indefinite word or usage.
WATER =AS-S FOR IRZUGATION.
The meteorologist measures the rainfall by the vertical
bpth of the equivalent layer of water that falls into the
nouth of his gauge. Assuming that the catch of his gauge