282 MONTHLY WEATHER REVIEW. FEBRUARY, 1912
EFFEUl! OF ABNORMAZ WEATHBR CONDITIONS DURING THE
CONSTRUCTION OF THE LOB ANGELES AQUEDUCT, AB-
STRAOTED FROM REPORT OF THE ENGINEERS.
By ALEXAXDEB 0. MCADIE, Proiessor U. 8. Weather Bmeau.
As mi ht reasonably have been anticipated on construc- tion wor 5 stretchihg over a distance. of 213 miles, there have been many accidents, though most of them have been comparatively unimportant. In only two instances
have substantial failures of work occurred, and these were due to extremely unusual weather conditions, and not to defects in plan, workmanship, or materials. I n
July, 1911, while constructing the concrete regulating ate in the a ueduct, just below the point of diversion
from Owens aiver, the river reached a height unknown for more than 30 years before, probably on account of the
melting of a large body of snoy in the mountains. By reason of the uncompleted condition of the work and the eenness of the cement just placed, the flood waters
. goke under and around the gate and ran down the canal for about 5 miles, where they were turned out and flowed back into the river. As soon as the flood subsided the
gate waa replaced, and additional constniction in the way of sheet-steel piling and concrete shut-off walls, suggested by the experience from the flood, was put in. The total
amount of damage to the work hardly exceeded $1,000;
the additional construction mentioned cost about $3,400.
The other failure of work referred to occurred at the
Point where the aqueduct crosses what is known as Tehachapi Wash, about 3 miles north of the town of
Moave. A section of conduit about 1,200 feet in length
had been built across a delta composed of sand, gravel; and bowlders, which had been carried by flood waters from TehachapiCanyon. As tifterwards ap eared, thismaterial,
though laid down by natural bydra up ic process, had been left in an uncompacted condition, due to the rapid passage of the carrying agency. In the summer of 1910, after the
construction of the section of conduit mentioned, a cloud-burst occurred in Tehachapi Canyon, resulting in a flood of water which ran down over the delta to the aque- duct work where its passage was obstructed b the dump ,
made by tke steam shovels on the lower side o P the trench
This caused the water to back up over the work to a de th of several feet, where it stood long enough to thoroug H y saturate the ground around the conduit, and thus caused a subsidence of the formation. The concrete was cracked
and fractured by this disturbance to an extent rendering to replace the work in the section mentioned,
$27,000. The cost of this reconstruction was somewhat excessive, due to the hardness and superior quality of the Concrete, which required heavy blasting for
its removal, holes bein drilled in the corners of every 2
stone for the making of the concrete for the new line.
*
feets uare and shotwit E dynamite. The broken concrete was t 1 en run through rock crushers and used aa broken
COVERING ALMOND TREES FOR FROST PROTECTION.
By AL-DEB a. MCADIE, Pmfesor U. 8. Weather Bureau.
In previous papers on the subject of frost protection it
was pointed out that one method of protection was by
. means of aper covers, a detailed account of which was ven in tEe Pacific Rural Press of December 24,1910.
!!he argument advanced was that such a covering would intercept the long heat wavea radiated from the earth on Uiet clsm hts, and that t h m would be a certain
 - s%eorr&ion o%e heat by the cover and a reernission: In brief, we could prevent a too rapid lrzss of beat by mter-
.?
%&
ference with free radiation, utilize the absorbed heat b reemission, and conserve the original heat sup ly of soil tree, foliage, and the stratum of air within 15 s eet of the :x+pT ground. The problem is a com licated one, as earth, tree, air,
the present we will neglect these points and give only and water vapor gain an B lose heat at varying rates. For
COVERED TREE WITH EXPOSED INSTRUMENTS ADJACENT.
the actual results df some experiments made during Feb- ruary and March, 1912, at the university farm at Dams, Cal. Instructor B. S. Brown had direct charge of the experi- ments, being assisted by Emile Grauel, orchardist. The
almond treeskbeing in blossom, it was decided to cover
ALMOND TREE, BEOWINQ. COVERINQ FOR TREE AND INSTRUMENTS INCLOSED.
one of them as shown in the illustration. The variety of the almond is the California Paper Shell. The paper
ft was again put on at 5 p. m. February 25, and removed
used was a weatherproof manila and was h t
. m. February 19, and removed at 9 a. m.
FEBBUABY, 1912. MONTHLY WEATHER REVIEW. 283
at 8 a. m. February 26. Again ut on at 6 p. m. of the 26th
was practic,ally impossible to put the cover on after dark, and it also developed that in a 10-mile breeze it took three men one hour to cover one tree: Two thermographs were used, one giqing t,he tempera- ture under the cover and the other outside. From t,liese
records it a pears that a minimum temperature of 19' F. occurred a P ittle after 8 a. m. on Mon~la~, February '76.
Under the cover the temperature fell to 2.4' F. Tliere is
a general resemblance in tlie curves, and while the teiii- perature under the cover was in every case higher t.han that outside, the difference is much less than was ant,ici- pated. It is plain that tlie loss of heat,, while retarded 1,.
the cover, was iiot sufficie,ntly tlecreastvl t o warraiit
extensive use of the met,hod in its present fowl.
Records of the humidity were also obtained, and these show the characteristic rapid increase in relative humidity during the frost period; thus at 4 p. m. February 35 the relative humidity was 20 per cent, at 6 p. in. 30 per cent, at 8 p. in. 45 per cent, nt 10 p. in. 52 per cent,, at, midnight
60 per cent, a t 2 a. m. 79 per cent, and then fluctuating between 80 and 87 per cent unt,il 7 a. ni., when there was a
rapid drop t o 70 per cent. Bet,weeii 3 and 4 a. ni. t,lirre
appears t.0 have been a slight gain in teniperat,ur$; that is, about 2' F., which mag possibly be connected mTth the latent heat of water, sinc,e in changing a pound of water to a pound of ice 143 British thermal units are set free. I n two .respects the ex eriment needs further study.
ence between the temperatures if there could have been introduced under the cover a small sup ly of wat'er
place, if a slow-burning heater G O U ~~ have been placed under the cover and near the vessel containing the wat'er we would probably have been able to prevent a fall below 35'. It may be noted that a t 4 p. in., nccording to the records, the weight of the water vapor per c.ubic foot was 1.702 grains, a t 6 p. m. 1.140 grains, a t 8 p. m.
1.282 grabs, a t 10 p. m. 1.223 grains, a t midnight 1.112
grains, a t 2 a. m. 1.418 grains, and a t 4 a. m. 1.54s grains. In a general way there wns very little water
va or resent. k n i l y , it was noted that the rise in temperature on
the various mornings, o.ft,er the minimum tempernture had been reached, was slower and less in degree under the cover than-in the open air. For example, the t'em-
perature rose 23' from 6 to S a. in. in the open, and only 18' under the cover. This is a matter of some impor-
tance, as. beyond doubt there is considerable clttnger t'o plant tissue when subjected to such a rapid warming nfter exposure to so low a temperature. The time of sunrise was 6.45. It has been suggested that in c.onnec.tion with the account of this experiment some data should be given regarding critical temperatures for various fruits a t differ- ent periods. While it is within tlie province of the meteor- 010 1st to furnish accurate data regarding the temperature
the work of the lant pathologist to determine critic.al temperatures. Tgus, ctccordin to Prof. W. L. Howard, the athologist of the Missouri gxperiment Station, after art' ll cially freezing thousands of peach buds, summarized the critical temperatures as follows: "Fully dormant peach buds can stand 8' or 9' below zero, Fahrenheit. When the are appreciably swollen zero is the danger point. d m the buds are showing
and left on until 8 a. m. Marc1 r 1. It was found t,hat it,
First, there would probaby s have been a greater differ-
heated to a temperature of about SOo. P n tlie second
of t B e air and the degree of saturation, it is more properly
pink they can st,and 1.5" above zero. When the buds are almost open 35" is the danger point. When they are newly o ened about 26' would be the point of danger.
cold enougli to cause uneasiness. When the petals are
off they c ~n stand 30' above zero. When the 'shucks'
(calyx lobes) are beginning to fall off, 32' is the danger point. ' The writer is not nwnre of any set of similar experi- nient8s covering nlmoncls. It, is lain from the actual esperiiiient,s niatle in tdie 0pe.n at Savis that a tempera- t,ure of 2-1' F. was criticnl, even though it last,ed but 40 niinr:t,es. Rrferrinx to t81ie nctunl record during the :hiontl experinieiit, given ~K J W , the t8emperat8ure was
helow 3.)" prnct,ic.ally froiii 10.45 p. 111. February 25
ririt,il 6.4.5 a. 111. E'elmiary 56. Moreover, the fruit after
sunrise R:H untler cover md snbjecte~l only t o a rise of
1s" (l'rom 24" F. to 4?o F.) in less tliitn one hour. The reitcler is referred t o an art.icle in the Pacific Rural Press, S y i l 30, l<)lo, ent,it81ect '' How much freezing fruit wi 1 ontlure, " for more tletailetl information
regarding t,he tlnnger point for apples. But, when nll is snit1 rtntl done, t,emperature da.t,a, while inst,ruc.tive niid in a way meeting the needs of the fruit
grower, do iiot t8ell tlie whole st,ory. The thermometer
may give the t,emperat,ure of the air, but the temperature of the tree or t,he temperature of the soil may be different. Then, again, t,emperature varies with height above the ground, nncl n n instrument placed a t the top of a tree may give much liiglie,r tempertitmiires than an instrument plac.ed in the micltlle of a tree or st>ill lower and nearer the ground. Fiirt,lierniore, tdie freezin point in ordinary
Centigrade scale, is not necessarilv the freezing point for water in the plant. S s W. N. h a w points out, it is the freezing point of water in tlie laboratory under care- fully organized conditions. It is not the freezing point of water. tlirtt covers four-fift,lis of the globe or of that in the harbors periodic,ally b1oc.ke.d with ice. It is not the
freezing point of tlie water contained in tlie cells of plan&, which is probably different, 111 different plants. Shaw
instances one plant w-liere it is 11* below 32'. In other words, the change of wat,er from t,he liquid to the solid state is dependent, upon certain physical conditions. Finally, tbe writ,er w011lcl call a.t,t,ent.ion t,o the difference
bet,ween freezing as c.ondiict8ed mtificially in the labora- tory and the freezing yhicd takes place in the open. .
I n future esperiment,s it will be necessary to take into nc.count t,he rate of warming up nf ter the blossom or
fruit has been subject8ed to a freezing temperature. So
far as we know, t8he present experiment of the covered almond tree n t Davis is t)he first one in which records
are available showing a difference in the rate of warming
up. According t<o t'he record, t,lie cover did not prevent rapid warming after sunrise, which was contrary to our expectation. While there was a difference between the inside and out,side rat8es of warming, we are of the opinion that in this experiment, a t least, the rate of warming was still t,oo rapid. In some way the cover must be improved, so as t80 iiiterpose a more effective barrier to insolation. This c.an be done by making the
cover double, with an int'ervening air space. I n conclusion, while the almonds were lost, enough has come out of tlie experiment to warrant the statement that with pro er care and improved methods fruits can be protected H rom the strains incident to rapid loss. of temperature and rapid heating, within moderate lirmts.
When t i e P pet,als are heginning to fall 2s' above zero is
use, that is, 33" on the Falirenlieit, sc,a 7 e and zero on the