SEPTEMBER, 1896. MONTHLY WEATHER REVIEW. 341
tions (and they certainly are of tlie highest importance when
we try to consider all the features of time and duration, in-
tensity, and direction and the attending noises) still, owing
to the fact that observers are generally taken unawares, the
Editor must urge those persons, and especially those institu-
tions that 'can afford to maintain a Weather Bureau seismo-
graph, to contribute thus greatly to our knowledge of this sub-
ject. In the annual report of the Chief Signal Officer for
1875, pages 374-377, the Editor submitted a few suggestione as to the observation of earthquakes. Among the apparatue
for recording direction the following suggeetion may be worth
considering : The linear extent of the horizontal movement of
the earth may be computed from the movements of several heavy balls of diflerent diameters and moments of inertia
rolling or sliding on a perfectly horizontal plane. The plane
should be strewn with a fine powder that will serve to mark
tlie path of each ball. The balls should be covered with a
very thin layer of some lubricant, such as tallow, to which
the powder will stick if the hall should roll. The plane should
have a rim and a glass cover to exclude dust and wind. Every
detail of the motion of the balls will thus be recorded on their
own surfaces and that of the plane. The horizontality of the
plane must be determined after the earthquake shock as well
as before. The balls must be as truly spherical and homo-
genous as possible, and, in order to secure dieerent sizes and
densities one might: for ecoaoniy7s sake, use the steel balls of the bicycle axles, the best of agate marbles, billiard balls of
ivory and the Japanese spherea of quartz crystal. From the
recorded movements of these balls one may deduce the direc- tion and force with which they were projected from their ori-
ginal position of rest by the earthquake shock, hut the com-
putation, of course, involves a knowledge of dynamics.]
FROSTS IN SOUTHERN C B Z I L F O ~-T ~ PREDIC- TION AND PREVENTION.
The following article from the Los Angeles Express of Jan-
uary 4, 1896, presents the valuable results of much experi- ence in that region, and may apply, with slight modifications,
to some other portions of the country :
One of the most reliable horticulturists of this section, James Boyd, of Rivewide, has laid down some rules bearing on this subject, in the Press, that are interesting, and their correctness is vouched for by years of experience and observation. He states that, as a matter of fact, the thermometer has seldom been known to fall between sunset and sun- rise more than 10' in a cold wave, or. say, to make sure, from 7 to 8
o'clock at night to the same hour nest morning. For instance, if the thermometer is above 40' at 8 o'clock at night, it need not be cxpected to fall below 30' before the liest sunrise, although sunrise Nometinies witnesses a fall of a degree or two for a few minutes, which usually does but little harm. A ain, if the wind blows all night, no matter how cold it feels, it will not freeze to hurt anything in the orchard; but if the north wind blows cold all day and dies down about sundown, with snow on the San Ber- nrrdino Mountains, it is well to prepare for the worst. But, again, if the barometer is low there will not come a destructive freeze. All of our injurious frosts have come with an exceedin ly high barometer, and, np matter how much it may threaten, the cofd is not likely to be excessive. The thermometer may stand for hours below the freezing point without freezing the fruit. If, on cutting the fruit, the juice flows freely it is not damaged. It must not be forgotten that it takes a much greater degree of frost to freeze a mixture of salt and water or sugar and water than of pure water, which fact is what eaves the fruit; and preen fruit is much more easily daiiiaged than thatwhich is ripe; a fact that is demonstrated every season in our vineyards, where immature gra )e8 will be frozen while ripe fruit will be untouched. 'llhere is one other point that may be laid down aa a certainty, and that is, that the thinnest film of haze overcasting the sky will imme- diately raise the tem erature several degrees. It is better not to run water, except when a[ signs point to a eneral freeze, for undoubtedly niuch harm results to the orchard, an3 also to the fruit, from having thc ground saturated for days, or even weeks, at a time, for rain usually follows any cold spell in a few days, and the constant wetting of tlie soil is very apt to produce puffy fruit later on.
RATE OF ADVANCE OF RIVER FLOODS.
The rate a t which river floods advance down the stream must, of course, depend upon the nature of the bed of the
REV-3
stream and the extent to which -its banks overflowed. The
cross section of the flood of water beconies so large in the low-
lands and flats that the forward advance is correspondingly small, and, in fact, every broad piece of overflowed bottom
land becomes a pond, temporarily, in which waters may ac-
cumulate, and thus diminish the severity of tlie flood in the
lower parts of the stream. Each stream has, therefore, pecu-
liarities of i t s own and demands a special study. The rates of advance derived from the study of one river can not be ap-
plied to another without material multiplication. As, how- ever, detailed studies upon river floods have as yet been made
in only a few river valleys, we submit the accompanying re- port, extra.cted from the proceedings of the Rochester Academy
of Science, as illustrating the class of work that might profit-
ably be repeated by engineers, for the snialler rivers at least,
throughout the country. When we know a t what rate the small rivers feed the larger ones we shall be better able to
study the floods in the latter.
Mr. J. Y. McClintock, surveyor for the city of Rochester,
having returned from an examination of the Genesee River
in May, 1894, gave an address, of which the following is n.
summary :
We have lately seen in the Genesee Valley the third greatest flood that haa occurred for thirty or forty ears. Studies have been made to determine at what rate oP speed t i e height of the flood traveled from Mount Morris to Rochester, and as this flood ran reat enough to cover the broad flats it gave a good example. I founj that the flood was at its height as follows: Mount Morris, May 21, 3 a. in.; Genesen, May 21, 13 m.; York, May 23, 9 a. in.; Avon, May 23, G a. in.; Rochex- . -. . -.
ter,-Mk 23, 3 p. m. The dstances down the general course of the valley are as follows: Mount Morris to Geneseo. 54 miles: Geneaeo to York. 3 miles: York to Avon 53 miles; Avon to Rozhester, 18 miles. This shows that the flood starting from Mount Morris moved at the following speeds: To Geneseo, 0.6 mile per hour; from there to York, 0.14 mile er hour; from there to Avon, 0.21 mile per hour; and froin there to iochester, Court Street dam, 2.25 miles per hour. The total time from Mount Morris to Rochester, 59 hours. Apparently the velocity increases faduallv, although not regularly, de ending upon the width of the va ey, which is very much narrower bePo6 -4von than above, and affords less storage capacity. From our observations at Rochester we had come to the conclusion that the flow of water during this flood was nearly one-third less than the flow of 1565, when so much damage was done. I was able to verify this conclusion by interviews with old residents at various poinG aloiig the river. At York the high water of 1865 waa about three feet abow that of 1894. At Avon it was somewhat over two feet above. One other important point was as to whether the great flats would furnish storage room for the flood below the surface of its grrmnd t n any such extent as is usually assiimed. This I was able to learn 11y
ocular demonstration. The river banks proper are general1 quite stee of clayey soil, from 8 to 12 feet high, and aa the level of tKe river ha? fallen from 13 to 15 feet within a few days, the ground has not had time to dry out, but was exuding water from its whole surface. This showed that the flats act as a great stora e. The importance of this will be shown by Mr. Rafter in his fortkoming report on the roposed storage dam. He will call attention to the fact that the 60 to 88 uare miles of flats when soaked with water will hold far more than x e great reservoir to be made.
STORM WAVES ON THE GRmT LAKES AND THE OCEAN.
The waves that occur on a body of water are of several
kinds and origins. We speak of short waves and long waves when we have in mind those that can l)e seen in their whole
extent from any ordinary point of view. The lengths of such
waves, from crest to crest, vary from a few yards to a mile.
We speak of a ground swell, or a long swell, when the rise
and fall of the water is but a few feet, and takes place so
gently that we scarcely see it as a wave on the surface of the water, but either feel it by the motion of the vessel or recog-
nize it by the character of the surf. The small waves due to
light winds, or to the interference of two opposing currents
of water, are generally known as ripples or rips; there is,
however, a still smaller wave known as the capillary ripple,
which does not concern us here. Some forms of ocean swell
are due to distant storms whose violent waves have, in the
a
MONTHLY WEATHER REVIEW. SEPTEMBER, 1896
course of 1,OOO miles, subsided into long and gentle swells.
Other forms of ocean swell are due to earthquakes or volcanic
eruptions that produce a great commotion in some central locality whence the wave spreads in all directions. The long-
est and gentlest wave is the primary tidal wave which is the
soirce of the ordina y tides in harbors and gulfs ; this pri-
mary wave has a central height of only a few feet in mid-
ocean, and would have a length from crest to crest of half the
circumference of the earth, were it not for the interference
of the continents. The tidal wave advances westward a t the
rate of 15O of longitude per hour. All waves, including the
tide, become shorter and turn into breakers when they reach shallow water. All waves are reflected from the shore line as
a wave of sonnd would be from a stone wall. By conibin-
ing together several small waves there may result a special
great wave. When a broad wave meeta and passes beyond
an obstacle, the deflected waves interfere with each other in
the rear of the obstacle.
The bottom of a lake may be so shaped and so adjusted
to the water i t contains that the distance from one side of
the lake may be exactly one-half of the wave that would naturally be formed in water of that depth, so that the water
in the lake can be set into such a wave motion that as it goee
down on one side i t rises on the other andvice versa. In such
cases observers on opposite sides of the lake simultaneously record high water and low water, respectively. This class of
waves was first observed in certain lakes of Switzerland, where
these waves were known as ‘L seiches,” but similar phenomena have been observed in all other parts of the world. This
French word indicates adrying-up or retreating of the waters
from the shore line, which retreat or apparentdrying up may
last for several hours, as a maximum, down to several minutes, as a minimum, depending on the dimensions of the lake. If
such a phenomenon, or any similar long and slow wave should
pass froni one end to the other of any one of our large lakes,
the amount of rise and fall a t either end would depend largely
upon the configuration of the sidee and shores of the lake.
Another class of waves is due neither to tides, earthquakes,
nor winds, but to changes in barometric pressure. We ordi-
narily measure-the pressure of the air by the height of the
column of mercury in the barometer, which is supported by the pressure a t the open end of the tube, and when we speak
of a pressure of 30 inches of mercury we really mean a pres-
sure of about 15 pounds to the square inch, so that each inch of the mercurial column may be considered as representing a half pound of pressure to the square inch. If for mercury
we should substitute a column of water it would need to be
34 feet high, as in the water barometer first made by Otto
Guericke in 1650 a t Magdeburgh. If, therefore, the baroniet-
ric pressure is one inch higher or greater a t one end of a lake
than a t the other, there is a decided tendency for the water to sink under the heavy pressure and rise under the lighter. Of
course, in the free air, such differences of pressure can only
exist in connection with a system of winds, and, therefore,
the so-called barometric wave is generally of less iniportanco
than those due to the direct action of the wind.
It is important for the student to carefully distinguish be- tween these different kinds of waves. Our progress in nnder-
standing and explaining the phenomena of nature and our
hope of predicting them for man’s safety, or utilizing them for
man’s necessities, all depends upon our correct appreciation
of natural causes and our understanding of the laws of na-
ture. As illustrating the confusion of ideas into which the
public and well-trained observers may fall, we may quote the
rise of water observed a t Duluth on Saturday, September 28,
when a storm center passed over or near the city. The mini-
mum pressure was 29.68 a t 8 a. m., reduced to sea level, while
the isobar of 30.15 skirted the eastern shore of the lake.
This difference of pressure of about 0.6 inch in a distance of
’
300 miles was, of course, accompanied by southeast to north-
east winds and rain over the greater part of the lake east of
Duluth. At the latter city the lake water rose from 2 to 4 feet, according to locality, and this was popularly spoken of
as a notable L L tidal wave.” Now, the fact is, that tides are
barely perceptible to close observation in Lake Superior, and
tidal waves of 3 feet are impossible. One correspondent ex-
plains the wave as due to the difference of barometric prese-
ure ; but a half inch of the mercurial barometer corresponds only to a half foot of water, and even this is much more than
could possibly have been caused by the barometric conditions
over Lake Superior, unless they had remained intact for sev- eral days in order to give the water a chance to move into a
position of static eqnilibriuni. Even if such static equilib-
rium should occur, the water would need only to rise a quor-
ter of a foot over the west end oE tlie lake in order to coun-
terbalance the depression of one-fourth of a foot a t the east end. But the rise of water observed at Duluth on Bepteniber 88
was not a case of static or barometric equilibrium, as the
reader will see a t once, froin the fact that the isobars rapidly changed their location and the great difference of pressure
soon disappeared. Sim’ilar unexpected rises and falls have sometimes been attributed to possible earthquakes, but this
hypothesis is probably always out of place in coniiectioii with
our Great Lakes.
There remains nothing but the wind as a probable cause of
the wave a t Duluth, and, in fact, the gale that prevailed on
Lake Superior, taken in,connection with the contour of the
shore line, is fully adequate to explain the phenomenon.
The explanations that we have given in previous numbers of
the MONTHLY WEATHER REVIEW of the floods caused by hurri-
caiies on our Atlantic and Gulf coasts, apply equally to tho high water observed on the Lakes. The wind drives the SUI-
face water forward, but when the water reaches the shore a d
begins to pile up, because it can no longer go forward, it then
returns toward the sea by flowing either to the right or to the left, or downward and backward, as an undertow. This for-
ward flow above, and return flow below, is maintained Ly the
wind in such a way as to constitute dynamic equililwium, but not static equilibrium. If we had to consider only static
equilibrium, we should find that a gale can support the pressure due to the weight of only a few inches of water ; but
in dynamic eqnilibriiim, the steadily blowing wind is per- petually communicating to the onward flowing water a small
amount of force, which the latter uses up in overcoming the
resistances (such as friction, the so-called viscosity, and the
inertia of slowly moving masses). As the undertow flows
backward, the forward or surface current has to rise over
the underflow, and the work required in order to do this is
done by the force that the wind communicates. If the wind
blows steadily for a few hours there is established an almost
perfect equality between the force conimuiiicated by the wind
to the surface water a d the work done by the advancing
surface current and the descending undertow. When the
movements of the wind, the upper and tlie lower currents of
water, are all perfectly uniform, this condition is spoken of
as steady movement, a stationary condition, or dynamic
equilibrium. If the wind should stop suddenly the water
would, by its inertia, continue in motion until frictional re-
sistaiices could use up its slight store of energy, after which
it would lie still and the upper surface would be horizontal ;
this latter is also a stationary condition, but it is static equi-
librium; there is no motion, therefore no frictional or other
resietances, and therefore, no dynamic manifestations.
The temporary rise and fall of water on our lakes must be
principally due to the wind. The disturbances of barometric
pressure, the fall of rain, and the tidal action of the sun and moon may contribute a very little to increase or to diminish
the influence of the wind, but the latter is the important cause.
SEPTEMBEB, 1896. MONTHLY WEATHER REVIEW. 343
These waves should, therefore, not be called LL tidcr.1 waves,” but, rather, L‘etorm waves” or “storin floods.” A similar
misnomer is noticed as to the heavy waves that sometimes unexpectedly occur on the Atlantic and Pacific coasts. Al-
though these waves are generally due to distant earthquakes,
yet they are often spoken of as “tidal waves,” whereas they should be called “earthquake waves.” The “ bore,” or wall
of water, resembling an ordinary breaker, but on an immense
scale, which advances up the deltas of many great rivers,
and is especially well developed in the Bay of Fundy, is a
destructive form of the tidal wave, while the gentle rise and
fall of the tide along the coast is the ordinary, quiet form of
the tidal wave. Another misnomer occurs in calling the
greatest and destructive waves of mid ocean “tidal waves” when they approach like an overpowering’ wall of water.
Thus, the steamer Propeso, when off the coast of Lower Cali-
fornia, on September 29, encountered a wave that swept her from stem to stern. This is designated as a tidal wave by the
daily newspapers, but was, properly speaking, a ‘L storm wave,”
being a combination of two large waves, or possibly a quge L‘breaker,’’ but not in any sense tidal.
We note here that the newspaper press reports of ’‘ damag- ing tidal waves ” in Duluth Harbor on the 14th and 20th of
September, 1895, were quite erroneous. The only important high water at that place was that of the 28th, according to the report of K. W. Brown, local forecast official, Weather
Bureau. On Lake Ontario, however, there was observed on
September 18, between 6 and 7 a. m., at Charlotte, N. Y., a
fall of about one foot, followed by a rise of one foot. A t some points on the sloping shore this recession of one foot
may have corresponded to thirty feet of the slanting beach, and thus a wild paragraph ‘( water receded thirty feet ” was
made to startle the country. Ingenious reporters even sug-
gested that this wave in Ontario had come all the way from Duluth through the Lakes and Rtraits, Ste. Croix River, and
Niagara Falls ; an impossible performance that makes the
suggestion seem ridiculous, although many took i t in all
seriousness.
ddETEOROLO(3IOAL TABLES.
By A. J. HENBY, Chief of Division of Reoords and Metmrologioal Data.
Table I gives, for about 130 Weather Bureau stationr
making two observations daily and .for about 30 otherr
making only the 8 p. m. observation, the data ordinarilj
needed for climatological studies, viz, the monthly meac
pressure, the monthly means and extremes of temperature
the average conditions as to moisture, cloudiness, movemenl
of the wind, and the departures from normals in the case oj
pressure, temperature, and precipitation.
Table I1 gives, for about 2,400 stations occupied by volun-
tary observers, the extreme maximum and minimum temper.
atures, the mean temperature deduced from the average oi all the daily maxima and minima, or other readings, as indi-
cated by the numeral following the name of the station ; the
total monthly precipitation, and the total depth in inches of
any snow that may have fallen. When the spaces in the
snow column are left blank i t indicates that no snow ha€
fallen, but when it is possible that there may have been
snow of which no record has been made, that fact is indi-
cated by leaders, thus ( . . . . ).
Table I11 gives, for about. 30 Canadian stations, the mean pressure, mean temperature, total precipitation, prevailing
wind, and the respective depart-urea from normal values.
Reports from Newfoundland and Bermuda are included in
this table for convenience of tabulation.
Table IV gives, for 29 stations, the mean hourly tempera-
tures deduced from thermographs of the pattern described
and figured in the Report of the Chief of the Weather Bureau,
Table V gives, for 28 stations, the mean hourly pressures aa
automatically registered by Richard barographs, except for Washington, D. C., where Foreman’s barograph is in use.
Both instruments are described in the Report of the Chief of
the Weather Bureau, 1891-’92, pp. 26 and 30.
Table VI gives, for 136 stations, the arithmetical means of
the hourly movements of the wind ending with the respective
hours, as registered automatically by the Robinson anemom-
eter, in conjunction with an electrical recording mechanism,
described and illustrated in the Report of the Chief of the
Weather Bureau, 1891-’92, p. 19.
Table VI1 gives the danger points, the highest, lowest, and
1891-’92, p. 29.
mean stages of water in the rivers at cities and towns on the principal rivers; also the distance of the station from the
river mouth along the river channel. Table VI11 gives the maximum, minimum, and mean read-
ings of the wet-bulb thermometer for 135 stations, as deter-
mined by observations of the whirled psychrometer at 8 a. m. and 8 p. m., daily.
The difference between mean local time and seventy-fifth
meridian. time is also givep in the table.
Table IX gives, for all stations that make observations at
8 a. m. and 8 p. m., the four component directions and the
resultant directions based on these two observations only and without considering the velocity of the wind. The total
movement for the.whole month, as read from the dial of the
Robinson anemometer, is given for each station in Table I. By adding the four components for the stations comprised in
any geographical division one may obtain the werage resultant
direction for that division. Table X gives the total number of stations in each State
from which meteorological reports of any kind have been re-
ceived, and the number of such stations reporting thunder-
storms (T) and auroras (A) on each day of the current month.
Table XI gives, for 38 stations, the percentages of hourly
sunshine as derived from the automatic records made by two
essentially different types of instruments, designated, respect-
itrely, the thermometric recorder and the photographic
recorder. The kind of instrument used a t each station is
indicated in the table by the letter T or P in the column fol-
lowing the name of the station.
Table XI1 gives the records of hourly Precipitation as
reported by stations equipped with automatic gauges, of
which 37 are known as %oat gauges and 7 aa weighing rain
and snow gauges. Table XI11 gives the record of excessive precipitation at
all stations from whish reports are received.
Table XIV gives a record of the heaviest rainfalls for periods of five and ten minutes and one hour, as reported by
regular stations of the Weather Bureau furnished with self-
registering rain gauges. Additional information concerning the tables will be found
in the January, 1896, REVIEW.