64
ISYS.
May ................................................ June.. ................................... J u l y ., ................................. August .........................................
Oduher ........................................... Novemkr ..............................
December. ......................................... IUYB. January ................................. February.. ............................. March ................................. April., ............................. .I
May ....................................
June ................................... July .................................... August .................................
September .............................. ., Ocmlier ................................. November ...............................
December ............................... 1YUU. January.. ............................... February ................................ 'March.. ................................
September .....................................
MONTHLY WEATHER REVIEW.
Inches.
+ 1.34
.I.. ..... ::
- 4. 2u
- 2.05
- 1.110
- 1. !I4
- 0 .5 1 l
- (1.40
- 1.6(l
- 0. 5lJ
- 1.35
+ 1.54
- 4.85
- 2.91
~
2.46
- 4.56
- 1.60
+ 0. 7s
FEBRUARY, 1903
August ................................ Septrmlirr .............................. October ............................... No%.embri .............................. December.. ............................
1YII1.
Januwy ................................. Frtwuary .............................. March ................................... A p r i l .. ................................. m y ................................... Jiiile .................................... July .................................. August. ................................. Septeiiilier ............................ Ortaher .................................
Novrlilbrr ............................... Deceluber.. .............................. 190:'.
January ................................. February ............................... March ................................... April ............................................ May .................................... June ................................... July .................................... August.. ................................ Septeinlrrr .............................. October .................................
NOVeIUlJcr ...............................
warm fall. Carrying comparisons back to 1898 shows that
predictions of rainfall and temperature in New England can
sometimes be made from the preceding temperature of Hono-
lulu. But it is interesting to observe that when this 60-day
rule does not apply, the temperature at Honolulu is followed
sisty days later by a similar temperature in New England 14
times out of 18 in the four years or 78 per cent. Excluding
four months of comparisons, affected by uncertain normals, 31
out of 44 or 70 per cent of months of observed temperature
a t Honolulu were followed two months later by similar changes
in New England.
TABLE l.--Depnrtures frowi monthly normclb i)i HoiioIdtt.
:. .......... - 0. SO
+ 4. $2
+ 5. i s - 3.01)
- 0.10
+ 2.00
+ 0. R2
+ 0.30
+ 0. 2::
- 0. I I J
~
0.27
- 1. 09
- 1.19
+ 1. ti8
1 1.68
I;. 06
- 2. 80
- 4.42
+ i. 91:
- 1.34
- 0.3:
+ 1.(1;
- 11.24
+ 0.2t
- 0.1;
f 4.65
Year a h irrviitb.
- 1. i
+ 1 .0
+ 11. 2
+ Il.li
+ 1.5
I,,ehrr. t (I. 4!l
~~
0. 21)
IJ. 5'2
t 1. 1>2
-- (I. 36
t 2.7s
+ 1.x?
-- 1. (18
- 11. 29
-t 11.30
+ 2.91
- 1, x3
- 2. I11
0. 00
I). 011
.~ ","(i
+ 1.41
- 1.67
~- 1.76
~- 1.41
+ 0. il -i :j. 69
-t 1.6s
~~
1.19
+ 0. 24
- (I. 14
- I . G4
~~
1. $1
- 1. :;0
(I. IJII
I 1.Ai
~~
1.34
-- 1.64
- 2.4s
-I- 1.91
~~
O.!II
-- 0.43
-1. 1.66
-~ l l .!l i
- 1. r2 - 0.54
-1 -1. I I X
-.
I; !
-1 I I .G l i
- 1.17
- I.*?
- 0. ii
~~ I). I??
-1 2.15 -1 1.35
~- 0.!IY
..........
~ ~~
....
F.
- 0 . !I
- 0.7
+ 1.2
+ 2 .7
i- 2.6
t 2. Ij
0. II
- 1. :;
+ 0. 1;
- 2. I)
- 1. 1
+ 1.1)
i 0. 4
I 1.5
0. IJ
I (I. :$
- 1.4
'r :i. 1
0. I1
J- 3, 7
+ '1. 1
A (I. 2
~
2. 2
- 1.2
~
2.2
' 0. ?(
t 1 .7
I 2. I 1
I 2. x , 5. R
1 2. !I
~
1.;
(1. 0
- 5. 1
+ I). 5
- 1.11
- 0. i 4- 0. !I
+ 2 .6
i 1. 7
-1 1 .2
1 1. i
~
4. 4
~
11. s
- 0. 2 I 0. 3
I ,. R
I 2.11
- 1.2
- 3. 6 '1. 5
2. 3
+ 1. 3
+ 1 .3
+ 4,s
........
It would seem, therefore. that there is a certain interval be-
tween Hawaii and New England by which mont,hly clinia-
tological preclictions may be approsimated to a consideralde
degree of accuracy.
NoTE.-The above table is as given by A h . Elmer without
being revised by the Editor. If the rainfall hac1 been es-
pressed as percentages of the normal annual amounts and the
temperatures had been expressed as percentages of the normal
annual fall at the respective stations, t,he comparison woulcl
have been even more interesting. Any improvement or change
in the adopted monthly normals mill change the positive and
negative signs, and also the above rule as given by Mr. Elmer.
His conclusions, therefore, may not be confirmed by further
investigation, but some definite geographic corelation of value
may result.-&.
SOME HIGH WIND RECORDS ON THE PACIFIC COAST.
By Pruf. ALESANDER G . MCAIIlE aud htr. \v. w. THIIMAB. Ollserver, United States Weather Bureau, dated May 27, 190".
A t the beginning of the year 1902 a new Weather Bureau
station at Point Heyea Light was completed. The station is
located in latitude 38' 12' north, longitude 122' 51' west of
Greenwich. The station a t this point was originally in rooms
of the United States Light-House Building, upper southwest
corner, and the records go back to October 9,1888. The first
observtition in the present oflice was on January 17,1902. The
elevation of the new building is &)C) b e t above sea level. The
height of the anemometer cups above the ground is 30 feet.
On February .23, 24, and 25, 1'302, a sei-ere southeast disturb-
ance prevailed along the coast of California. This was the
first pronounced disttwbance to which the new station had
been subjected. The following extracts from the Daily
Journal a t Point Reyes Light by the Obrierver, Mr. TV. W.
Thomas, tell the story of the weather conditions at that time:
Febrimry 2,?, 190.--A southeast storm began during the night with
light rain ancl a 7O-iiiile wind; t h e storin continued thrvughout the clay
iowiiig no abatement a t nightfall. A maximum of 80 milrs from the
tiitlirttrt \\as recnriled a t 1:30 y . ni., and this relocity was rrachecl Ire-
Order to hoibt houtheast storm warnings
Februrtry 5, 13/t?-The day opened with light rain and a terrific south- east storiri ill ~~rogress: w i d inrreaswl rapidly to 90 miles an hour a t
11j.15 a. in. and wntinued a t that velocity until after 12 noon, very fre-
i1u"iitly reaching velocitiescif 98 to 100 miles an hour. d maximum of 98
niiles during five cwnsrcntive iriinuteq occurred 11:15 a. in., at which tiine
itn extreme x elouity of 11 13 miles was recorcletl-a mile in 35 becnnds. The \find I q a n to v e ~r to the weht aud to lose its force soon after noon; clear- a t 2 p. in. the weather was practically clear,
(1. Bliout 3 3. m. the cloridb began to increase ning threatening weather prel ailed with brisk
w ~u t l i n r k t wiiid. Dic.tant liylitiiiig wac. oliserved in the nnrthwwt between 11 and ~2
1'. in., ant1 later iiiformatinn s1111wed that dihtant thundrr and lightniug
~ic~.urrrd in the iiorthwest fregluently tlirouyhout thr night.
S1ii1.r the pashage o f this htnriii tht. eeather has readled a normal
vi )nclition.
During all thik terrific mind the aiieniometrr worked magnificently and
I i i I i i r cbf the instrument.: were d:imagrtl in the least.
On March 1 another severe southeast disturbance pre-
vailed off this section of the Pacific coast. A t San Francisco
the wind changed from sout,heast at 9 p. m., seventy-fifth
meridian time, blowing from the south for about 28 minutes
mid then froiu the southwest, reaching a masiiuuin velocity a
little after 10 p. ~n . uf 60 miles and an extreme velocity at lo:l2
11. m. uf 75 miles. At Point Reyes Light the maximum velocity
occurred at 9:45 1'. m., when 10 miles were recorded in a trifle
over five minutes. The observer states in a letter "that for R
half hour prior to this time he checked off the 10-mile spaces
as they occurred, timing the miles with his watch. One mile
was completed in slightly less than thirty seconds; and for
five minutes, including the time of the extreme velocity, the
miles averaged a small fraction less than thirty-three and one-
half seconds." This is at the rate of 107 miles per hour. The
following lwief report of the storm was written by the observer,
Mr. W. W. Thomas:
The (lay oIwnetl with cloudy, threatening weather and light wind vary-
ing in tlirection from wulheast t n northeast. Light rain began at 7:45
a. in., I w d time: wind continued light to fresh, northeabt to southeast
in, when it lwgan lllnwing qteaclily from the southeast and to in-
I fon.e to aliout 45 miles an hour. At 3:30 p. in. it increased sud-
a little more than 'ill miles an hour. Light rain ended at 5:35 p. 111. ancl at 5.55 p. 111. a rainhow wa4 obseryetl. Ahout 5:3U p. m. the
winal began to veer to the wehtwarcl and to iiwreahe rapidly in force. A t
6:45 1). ni. a niasimum of 1118 miles was recorded from southwest. Wind cuntinurcl to veer to webt and northwest, still continuing at about 100
niilrs an hour until !> 11. in., local time.
Our flttgstaff (wontlw ) blew down at 6:45 p. in. and the receiver of the rain gage blew away and has not been found.
i t l j during the afternoon.
I \ ril 12 noon. Line down since 12 noon. No communication east.
FEBRUARY, 1903. MONTHLY WEATHER REVIEW. 65
FIG. 1.-Weather Bureau building at Point Reyes Light and the old flag staff, blown down March 1, 1902, after standing for several years.
The flagstaff blown down is shown in the accompanying
photograph (fig. 1) made by Professor McAdie on December
28, 1901, just before the building was ready for occupancy.
It should be stated that this flagstaff had stood for several
years, being used for signaling purposes, and was, so far as
one could judge, well braced and generally in good condition.
From May 15 to 20, 1902, the daily weather maps show the
existence of a marked depression over the Mexican boundary
and the valley of the Colorado. On Saturday, May 17, the
southern depression, merging into an extensive trough over-
lying the entire Rocky Mountain region, was followed on the
Pacific coast by an area of high pressure. While the readings
were neither very low nor yet very high, there appears to have
been an extensive air motion, an unusually large number of
stations reporting maximnm velocities. On the California coast
steady and extremely high northwest winds prevailed .for a
period of not less than seventy-two hours. At Point Reyes
Light for forty-eight hours ending midnight, May $3, the
average velocity of th,e wind was 72 miles; for the twenty-
four hours ending midnight, May 18, the average velocity was
78 miles; for twelve hours ending midnight, JVIay 1% the
average velocity was 84 miles; for six hours ending midnight,
May 18, the average velocity was 88 miles. The greatest
number of miles recorded in any one hour was 102, from
8 to 9 p. m., seventy-fifth meridian time, May 18. The maxi-
mum velocity for the storm was 110 miles, a t 8 5 0 p. m. of the
18th, and the extreme velocity 120 miles, at 8:38 p. m.
This record is so remarkable for its length, the high veloci-
ties involved, and the general character of the air motion that
a photographic copy has been made, accompanied by a partial
enlargement, 3.3 times the original, of the portion between 8
and 9 p. m., when the extreme velocity was recorded. Four
thousand seven hundred and one miles of wind are legibly
recorded, and the record is complete, except from 9:19 to 9:36
p. m., during which time the observer put a new set of cups
on the anemometer to replace a set that had become loosened
from the axis and carried away a t 9:19 p. m., May 18, the actual
number of miles for the hour preceding being 91.
It also appears that between 8 and 9 p. m. on May 19 we
have an actual record of 102 miles per hour. According to
the tables furnished on page 16 of Circular D of the Instru-
ment Division, the corrected velocity corresponding to this
observed velocity would be about 77 miles.
It is not known to the writer how this record compares with
those made at other points. He has found, however, a record
in the MONTHLY WEATHER REVIEW for January, 1886, page 15,
which, referring to the storm a t San Francisco on January 22
giving a maximum velocity of 42 miles, states that the storm
was said to have given the heaviest wind in twenty-five years.
At Cape Mendocino, Cal., the writer finds, by reference to the
forecast charts at San Francisco, a record of 108 miles, from
the southeast, on January 22,1886, a t 7 a. m. There was also
recorded a maximum velocity of 144 miles, from the southeast,
at Cape Mendocino on January 20, 1886. The original wind
sheet, if it be in existence, is a t Washington, D. C., and it
might be interesting to compare that record with the present
one. In a table of the average velocity at Weather Bureau
stations and the highest velocities for a 5-minute period, the
Chief of the Weather Bureau gives 104 miles at Fort Canby,
Wash.; at Hatteras, N. C., 105 miles; at Galveston, Tex., 100
miles; a t Kittyhawk, N. C., 100 miles. The highest velocity
recorded at San Francisco is 60 miles, and at Eureka, Cal., 60
miles.
The following note relative to high winds at Mount Wash-
ington, N. H., is taken from the MONTHLY WEATHER REVIEW,
February, 1886:
The 8-hour movement of the wind from 3 to 11 p. m. of the 26th was
925 miles, being at the rate of 115.6 miles per hour, and largely in excess
of any previous 8-hour movement ever recorded at this station. The total movement of the wind for twenty-four hours ending 3 p. m. of the 27th was 2673 miles, being 533 miles in excess of any previous 24-hour
movement. During the night of the 2627th the terrific hurricane caused the building to rock and tremble; huge masses of frostwork were dashed against the station building with reports as loud as the discharge of a
cannon.
The wind records a t Pikes Peak have been published, but
the volume is not accessible to the writer.
66 MONTHLY WEATHER REVIEW. . FEBRUARY, 1903
within 50 miles of port, the strong northwest wind drove her
nearly 1000 miles to the southward. It required ten days to
make port. The following is a statement by Captain Neville:
I n connection with this high northwest wind of May 16-19,
it only remains to be said that at San Francisco during the
same period there were recorded 1311 miles, distributed dur-
ing each twenty-four hours as follows: 415, 411, and 485.
From 6 a. m. of the 18th to 6 a. m. of the 19th 531 miles were I I
recorded.
At Point Lobos (see fig. 2), the extreme northwestern end
of the peninsula on which San Francisco is situated and about
five miles west of the Mills Building, the following velocities
were recorded: May 16-17, 586 miles; 17-18th, 890 miles;
18-19th, 938 miles, or for the entire seventy-two hours, 2414
miles, which is about 33 per cent of the air movement at Point
Reyes. Between 9 and 10 p. m., May 18, 53 miles were re-
corded; maximum 5-minute record, 72 miles, at 7 p. m., May
18. On Mount Tamalpais, Gal., for the three days under con-
sideration the velocities were 1096, 1123, and 1002 miles, re-
spectively, or in all 3121 miles, being 44 per cent of the Point
Reyes movement. The maximum velocities were: May 16, 86
miles; May 17, 75 miles; May 18, 69 miles, and May 19, 69
miles.
I
FIG. 2.-United States Weather Bureau station and storm-warning
tower, Point Lobos, Cal.
With reference to the actual velocities experienced by ves-
sels, it is interesting to note that the steamer George W. Elder,
leaving San Francisco on the morning of Sunday, May 18,
found it impossible to pass Point Reyes Light and had to put
into Drakes Bay for fourteen hours. In the same place the
Elder found the big Kosmos liner Serapis, a collier, and a fleet
of schooners; none of them had been able to get around the
point.
Of even greater interest is the experience of the British
ship Westgate, which arrived a t San Francisco May 27, after
being driven 1000 miles out of her course. On May 17, when
FIG. 4.-Water tank on bluff at Point Reyes carrying the ane-
mometer at the time of the high wind of May 18, 1902. Point
Reyes Light is shown to the left of the water tank and below it, on the bluff next beyond.
We left Newcastle, Australia, for Ban Francisco ninety-two days ago
with 2084 tons of coal. It was one of the most uneventful voyages I ever
made until we were within 750 miles of San Francisco. We encountered nothing but light winds and calms all the way, but nevertheless we made
fair time. When about 750 miles from port the weather began to get
dirty. Still I thought we could make our distance and run in through
the Gate before the storm broke. I was mistaken. When within strik- ing distance of our destination the storm came down and we had to 'bout
Fmauna~, 1903. MONTHLY WEATHER REVIEW. 67
ship and run for the open sea. I n all the years I have been to sea, I
never saw a gale to equal the one of May 17 and 18. Mountainous seas
broke aboard and the ship labored so heavily that at times I thought she would roll the masts out of her. The lower topsail and foresail went out
of the boltropes like a kite escaping from its anchor, and for a time the ship ran under bare poles. After two hours hard work we got a goose-
winged lower topsail set, and under i t the Westgate rode out the storm.
From that day to this we have had nothing but light winds, calms, and
fogs. * * * We sustained no damage during the norther, except having whatever was movable on deck washed overboard.
On May 27, in connection with the paper above printed,
Professor McAdie submitted a photographic reproduction of
the anemometer record for May 16-19, showing 4701 recorded
miles in the three days, 17th, 18th, and 19th; he added an
enlargement of a portion of the record, showing 102 miles
recorded during the hour 8-9 p. m., of May 18, with a maxi-
mum velocity at the rate of 110 miles during the five minutes
8:47-852 p. m.
FIG. 5.-Water tank and anemometer at Point Reyes Light, as
seen looking west-southwest. Dimensions: Base of tank, 4
feet above ground; height of tank, 16 feet; diameter of tank
at the top, 19 feet, 3 inches; diameter of tank at the bottom,
20 feet, 6 inches; height of anemometer support, 10 feet, 4
inches; height of cups above ground, 30 feet; height of cups above sea level, 490 feet, approximately. The anemometer
support is placed near the western edge of the top of the tank.
A
FIG. 6.-Storm warning tower and new point of exposure for
the anemometer. Height of anemometer cups on the tower,
53 feet a b v e the ground and about 593 feet above sea level.
FIG. 7.-Plan of Point Reyes Peninsula, according to a survey made
in 1880 by United States Engineer Corps. 1. Fog signal station;
elevation 100 feet. 2. Light-house tower; elevation 250 feet. 3.
Steps and chute leading to the light-house and signal stations. 4.
Tank; elevation 460 feet. Anemometer on the tank; elevation
490 feet. 5. Weather Bureau building; elevation 490 feet. 6.
Location of the new storm-warning tower; the ground at the tower is 540 feet; the peak is 550 feet high; the anemometer on the tower
is about 593 feet above sea level. 7. Residences of the keepers. 8. Highest point of the ridge; elevation 597 feet. 9. Life-saving
station.
FIG. 8.-Contour of Point Reyes, as seen from the northwest. 1.
Fog signal; elevation 100 feet. 2. Light-house tower; elevation
250 feet. 3. Steps and chute leading t o the light-house and signal stations. 4. Watertank; elevation46Ofeet. 5. Weather Bureau
building; elevation 490 feet. 6. Storm-warning tower; elevation of ground 540 feet. 7. Dwelling of light-house keeper. 8. High-
est point of the ridge; elevation 597 feet. A. Point from which
photograph C, or fig. 3, was taken. B. Point from which photo- graph A, or dg. 5, was taken. C. Point from which photograph
B, or fig. 6, was taken. D. Former exposure of the anemometer.
~
[The Editor regrets that these photographs as submitted can
not be reproduced by the half tone process; on the other hand,
any copy made by hand would lose the advantage of being a
facsimile reproduction. The records are remarkably clear and
uniform, so that there can be no doubt as to the accuracy of
the rate of movement.]
Under date of May 27 the Observer in Charge, Mr. W. W.
Thomas, writes as follows:
MONTHLY WEATHER REYIEW. FEBRUARY, 1903
In reply to your inquiry regarding the loss of the anemometer cups, I have the honor to say that I delayed further report upon this matter
with the hope that in the meantime I could flnd the cups and from their
condition report definitely as to how they gave way; however, the cups
can not he found and the defect that resulted in their loss must therefore remain a theory. The miles of wind were recorded with such rapidity
and regularity up to the very moment of the loss of the cups as to show
that the screw that holds the cups tu the spindle was coristantly tight, which dispels the theory that this screw had wnrked loose, thereby allo\% - ing the cups to he lifted off therefore, my only rflinaining theory ib that under the terrific and long-cnntinued htrain onv or more of thr crohs arim gave way and probably bent upward, which gave the w-ind a sudilrn.
highly increased power on the CUPb that snapped the screw above ref
to and instantIy releas the cups from the spindle. The anenioi
was not injured, aside 111 the l<lhS Of the CUph, and ill OrdPr to +'XI
the resumption of the ord, I left it eq)osed, simply putting on a IIW
set of cups.
The 20 miles of wind interpolatecl a t the time of the 1)reak
(9:19-9:36 p. m.) have been aclded to the dial. so that the dial
readings correspond to the record.
Under date of June 5, 1902, ancl in reply to the preceding,
Prof. C. F. Marvin wrote, as follows:
Inasmuch as the spindle i )f the anemompter ma+ intact aut1 tlie cu11h
entirely removed, I am inclinrtl tti think thil inuly plausilila oxplanation
)t
secured tight enough, tir iwuausr of actitm fro1 \\
backed off a little aud permitteil an upward gu5t to lift the cwp+
spiudltl. From the phi>tograylI inc1i)st.d with the reliort it i.; oIiviou+ that there Ill~lbt be a rrrj pronnuntvd ul~warcllq inclilied (lirevtion ta I thr \\ iuil
at the p i n t of exlmsure of the a ~i ~i i i i ~r i i r t ~r . thus f;u.ilitatin,y the lifting
ib that the cups. hy the action of the storm. were
dle, either because the wrew:. liinrliny tlie cwl)r
I-
Uiider date of June 27, 1902, Professor RIcAclie says:
along the coast, and also at a rlunilw of iiiteriibr point-.
NOTE ON THE ANEMOMETER EXPOSURE AT POINT
REYES LIGHT, CAL.
By c' F. nl IRVIN, Pmfeswr of M c ~w I ~~J ~o ~~. dater1 Fvhroar\, 190:.
Prior to the erection of the Weather Bureau lmilding to
accommodate the station a t Poiiit Reyes Light the anemoiue-
ter was exposed on a water tank located on the side of the
bluff. The ex-
cessive wind movement recorded a t this locality, as set fortli
in Professor NIcAclie's paper, preceding, led us tu question
whether this was not due, a t least partially, to a faulty es-
posure and to a strong draft of wind arouiid the point of the
bluff. I n order to secure information on this point. extensive
comparisons of wind movement have been conducted by in-
stalling a cliiplicate anemometer esposcd on an attachiiieiit to
the storm-warning tower erected very nearly on tlie s i ~~i ~~i i i t
of the bluff, as indicated in figs. 3 aiitl ti. The aneiuoiiieter
cups were about 53 feet above the ground at the base of the
tower-that is, about 593 feet above sea level. The anemome-
A view of this location is shown in fig. 5.
ter on the tank had an elevation of about 490 feet above sea
level. The relative location of these anemometers is more
clearly indicated infigs. 7 and 8, which give the approximate
plan and contour of the bluff.
The two anemometers were in all respects alike and recorded
automat,ically side by side on a special two-magnet register.
Comparative readings extended from noon, September 19,
1902, to noon, February 1, 1903. The following table gives
the t.otal nionthly movements for the two anemometers:
1.07 Oct*ilrer. .. . . . . . . .. .. . . . 14,466 Noveiubrr. .:- ..___ .. ..
.I
15.395
1
14,792
I % 1 :: 1 i:tz
~ ' i:::
~
i:.: 1
1.05
Ikwnilier. _. __ . __ __. . . 12,%35 12,225 1 58 53 1. 09 16.6 16. 4 1.01
January .... .. .. .___.. . 12,112 11,564 i 4 67 1.10 16.3 15.3 1.03
13,519
IYID.
The hourly readings were tabulated for the entire period,
but it careful examination of these fails to disclose any im-
portant results that are not also presented by the total
monthly movements. It is apparent,, from the tables, that the
memometer on the tank recorded from 1 to 'i per cent greater
monthly movements than the anemometer on the tower.
Eitoncled comparisons of anemometers at the Weather Bu-
reau have demonstrated that diflerences in the indications of
instruments that are of similar design and construction are
caused principally by inaccuracies in the lengths of the arms
of the anemoiiieter cups, that is, by ciifferencen in the mean
illstance of the centers of the cups from the center of the axis
of revolution.
In the case of the anenioiiieter cups used in the present
coiiipnrisons a t Point Reyes Light, careful measurements show
tlint the arnis of the tank anemometer are 0.015 of an inch
sliorter thnn those of the tower anemometer. This is a differ-
ence of only 0.22 per cent, that is, we ~h o ~l d expect the tank
anemometer to show one-fifth of 1 per cent more wind move-
iueiit than the tower anemometer.
The actual cliflerence found from comparisons of the record8
a t these two stations amounts to from 5 to 10 per cent for the
iiiaximuni winds and froiii 4 to 6 per cent for the monthly
in01 einents. and must be attributed to some peculiarity of the
erpobure on the tank and to the variation in the direction of
the wind.
From the foregoing i t niay be assumed that the extraordi-
nary mind belocities recorded during the storms reported by
Professor IIcAdie were fairly well indicated by means of the
anemoiiieter on the tank. In this connection, however, it is
necessary to reinark that accurate studies of the Weather Bu-
reau type o f Robinson's anemometer have never been extended
t u velocities aboxe 50 mile6 per hour, a t which speed the ve-
locity iuclicated 1 y the instrument is 9.2 miles or 18 per cent
too high, SO i t is very probable that the wind movement pro-
ducing an intiicatetl velocity of from 100 to 120 miles per
hour on the Weather Bureau anemometer was actually much
less than 100 wiles per honr. It is very greatly to be desired
that researches should be undertaken to evaluate the indica-
tions of our aneinonieters a t the very highest velocities ever
indicated.
COMPOSITE AND OTHER ARRANGEMENTS OF
WEATHER TYPES.
l h H \V I:ia 11 i i i i w b v , 1 ,o ~d Fan., ast o t k i a l , I ~i l u t l i , Miiiu., dntril March li, 1903.
Duriiig revent years conniderable attention lias been devoted
to the classification ancl indexing of weather maps and types
as an aid to the forecasting, the most prominent contributors