SEPTEMBER, 1917. MONTHLY WEATHER REVIEW. 468
mined for each va or at ordinary temperature, is: water
cent of the total vapor molecules present, which would correspond to about 100,000,340,000,190,000 molecules er cu. cm. These nonelectric molecules are characteristic for each vapor. Exposure of the va or-gas iiiixtures t.0
and thus the nuniberr) of molecules per nucleus, to 8 for water and 6 for alcohol; and increases also in particular their number very niuch, in accordance with the radiation intensity. Lenard’s theory supplemenbs Kelvin’s theory b adding a term depending on the ratio of the portion
and on the surface tension which varies with the radius and the thickness of t,he liquid shell. It also diffeis from J. J. Thonison’s theory in so far as with increasing es- pansion a supersaturation is said to be reached at ivhich all the nuclei are condensed; the total number of nuclei in water vapor (no esternal field) seems to be limited to lo5, as stated.--H. B[~omts].
1.9X lo-”, ethyl Bf coho1 2.5 X lo-”, benzene 0.8 X lo-” per
0 and y rahations, further increases t i e size of the nuclei,
o 9 the drop surface from which evaporation can t,ake place,
GT/. 57-3 ( 0 Y B ) A NEW EVAPOBATION FOBMULA.’
By R. E. HORTON.
[Rrprinlrd from Science Abstracts, Sect. A. 4ug. 30,1917,# i91.1
in180’Dalton deduced the foiiiiulaE =C(V-v), where E is the rate of evaporation froni a liquid surface, V the vapor pressure corresponding with. the temperature of the liquid, 27 the vapor pressure existing in the atmosphere at the time and C is a constant. The effect of the wind was allowed for by var ing the value of C. Later workeis
d o w for the wind speed ‘LV. According to the forniula thus modified, the rate of evaporation increases indefi- nitely with increase of wind, whereas in practice a masi- inum value is obtained when the wind velocity reaches 15
to 30 miles an hour, and above this there is no further increase. The author, therefore, prefers to allow for wind by the introduction of an exponential factor, and de- duces t8he equation,
E=C[(2-e-k-kw)V-Z’].
Values of the coefficient (2- ck”)rnay be read off from a graph thus simplif ing the working. The formula is
hunlidity condensation will take place in st,ill air, while there will be slight evaporation under the same condi- tions in a wind. This result has been verified in prac- tice. The formula as stated applies to a small liquid surface. The latt,er part of the paper is devoted to a consideration of the case of a larger area where the evapo- ration from the leeward part will be hindered by the presence of the vapor given off by theapart niore to wind- ward. The author states that it will, in many cases, be more accurate to calculate the rate of evaporation froni a large water surface by means of the formulaz here put forward, than to rely on attempts a t direct measurement with the ordinary type of evaporinieter.-J. S. Di[nae].
have usually intro d uced a factor of the form (1 +kw) to
also a plicable to t i e case of condensation. It will be seen t P iat under certain coliclibions of t.emperature and
6-3-/.*5-y8. / : 6 3 4 FORESTS-AND-FALL EXPEBIllbENTS. .
There appeared in Nature, for ,4u st 2, 1917 (pp. 445446), a review by Mr. Hugh R. Ell, of the recent
1 Engineering NBWS-ReCmd, New York, Apr. 26,1917, 7&196-199.
Indian Forest Bulletin No. 33 by M. Hill, chid c o d sioner of forests of the Central Provinces. Dr. Gilbert Walker of the Indian Meteorological Department con- tributed two appendices to that bulletin, and concerning
nr. Walker’s conclusions lfr. Mill says in part:
J?r. Walker considera that, aa Blanford pointed out in 1887, “the on1 mtisfactory evidence would be that obtained by comparing the rainhi of a district when well supplied with forests with that of the =me district when the trees were very few.’’ In our opinion the comparkn should not be that of a district A at the time t with the same district at the time t’; but to conipare the relation of district A to a contiguous district B at the time t with the relation of A to B at time t/. where A is a district that has undergone a great change 89 regards forest covering, while B haa remained unchanged. The reaeon for this indirect com- parison is. of course. to eliminate the effect of the two periods Mli in
what Prof. H. II. Turner calls different climatic chaptera. An%er method would be to deterniine the relation of the isohyetal lines to the conflguration of the land on wooded and treeless districts of mmileu character. As pointed out in the report on the rainf?ll in the Geolo ‘cal Survefs ‘. Water Supply Memoire of Hamphire, the district oathe Xew h e s t shows a considerably higher general rainfall than ita elevation above sealevel ap ears to suggest. The subject is bqth fascinating and important, ani the time will no doubt come when in- crease of accurate observations will enable the vague belief in the beneficial influence of forests on climate to be supported or corrected by detinite ineteorologicnl evidence.
It seems appropriate here to recall the circumstunce that precisely the first method here suggested by Mr. . Mill for adving the problem of the relations between rain- fall anfforestatiori was adopted by the United States Weather Bureau in 1910, cooperating with the United Stn tes Forest Service. These two services have selected two contiguous and practically inden tical watersheds in the Rio Grande National Forest (lat. 37’ 45’ N., long.
1 0 6 O 50‘ W., alt. 9,400-11,000 feet) near wagon Wheel Gap stittioil on the Denver & Rio Grande Railroad, at present under identical forested conditions, and have established therein a large number of thermometer, precipitation, and streani-gage stations. Careful obser- vations will be carried on in both watersheds for a number of Sears and a t the conclusion of t-his first period one
of the watersheds will he deforested and the same obser- vat ions continued for n second period corresponding to
the first one. Already we hare secured nearly a full 6-years’ record there, as observations actually began October 32, 1910. While the United States seems to have been the first to take this step, it is certainlydesirable that as many other countries as possible should make the same test. Mr. Mill, it is not likely that a m . area in UniteB States is sufficiently supplied with well-dist ributed raingages to encoura e one in undertaking the computational labor involvef-c. A., jr.
Concerning t8he second method sumvested b
EXCESSIVE PXECIPITATION IN LONDON, ENGLAND.
[Repintdfrom Nature, London, June 21,1917.99328J
Dr. H. R. Mill records, in the London Times of June 19, 1917, that the thunderstorm between 5 and 7 p. m. (summer time) a on Saturday, June 16, was, if measured by rainfall, one of the most severe ever experienced.in London. More than 2 inches fell over an area measuring 10 miles from Barnes to Finsbury Park and 4 miles from Hyde Park to Willesden Green. A t two oints within this area more than 3 inches was reportex-viz,
riment is described in detail in the MONTELY W E A ~E REVIEW, &p-
t S 2 %18:1453-1455. with map.
3 s18&m& Time.’* This is the first reference in the MONTBLY W Z A T ~E REVIEW to the ‘Ida light 1 use among Europesn countries ante 1916. “Summer time” in England is I s f a s t e r than QreenWich Mean Time. A presentation of the advantages and dlsadvantagas of “8ummer Time”. as develo ed bv a year of actual es erience therewith, wU he found in Review 01 Reviews,%ew kork, June, 1916, pp. ‘h5-716.-C. A., Jr.
scheme that has been in such
464 MONTHLY WEATHER REVIEW. SEPTEMBER, 1917
3.20 inches a t Cam den Hill, Kensington, and 3.37
inches a t Barrow dl, north of Regent’s Park. Such falls in a short eriod have only been exceeded in the
by 3.42 inches at Blackheath on ,July 23, 1003, and hg 3.90 inches a t Hampstead on April 10, 187s. On June
23, 1878, Mr. Symons recorded a t C’amden Square n fall of 3.38 inches in about an hour itnd 1% half; on Saturdny last the recording gage showed that P.SG inches fell in
2 hours, and no heavier rain has been recorded a t (’imi- den Square in the 29 intervening years.
London area, so P ar as Dr. Mill has been able to ascertain,
GREATEST 84-HOUR RAINBAIJa AT WASEINQTON. D. C.
It is interesting to compare with these very escep- tional falls under London’s conditions, the following equal1 exce tional falls under Washington conditions, from the records of the com iLd by Kdr. Herbert Was R ington office of the
Ciivcilest rriii!/irllw Jhr triiy .I.$ h r c s t i l k d i i i r q l o i i . [). f.‘.
Inches. Date. Remarks.
5.66 1Si4. Sept. 15-]ti.
5.00 1904. Sept. 14-15.
5.80 LS7S. J ~l y 29-30,
4.96 IS!% AUC. 12. ..
~
4.22 1805; Jill; r M . 3.26 in(-liee Cell in 1’’ Ism. 4.16 1886. June 22.
4.12 1876, July 30.
3.98 1877, Ort.. 4.
3.92 1905. hug. 26.
3.67 1910. Oct. 19-’%. Xot. n thiinderstorm fall. 3.50 1886, May 7-8. 3.48 1900. June 2. 3.04 inches fell in lh Sm.
3.27 1917. July 35. 1.90 inches fell in 1’1. .
3.34 1886, July 2ti-27.
- .
To this table must be added the remark that in 1906
2.46 inches fell within 56 minutes 011 August 34.-c. A., jr.
sr/. s/ (6 48) .
REVOLVING FLUID IN THE ATMOSPHERE.’
Iiy Sir NAPIER SHAW.
[Abatrflct of an address before the Royal Society. June 21. 19li.l
It is generally assumed, as appears prticularly froin n
recent paper bv Lord Raylei-h,2 with reference to a for- mer paper by Dr. J. Aitken, h a t the rnotioii of air in cy- clones and antmicyclones may be classed as the nlotioii of revolving fluid, symnietiical about a vertical asis. Reasons are given to show that this assum tion with
erroneous; that circular isobars on the ma do not indi-
revolvlng fluii would not be indicated by a system o
circular isobas. The next point for consideration is how a mass of revolving fluid traveling with a speed of
translation of the same order as the speed of rotation, and of sufficient size, would be represented on a ma . Dia-
gur cases for differelit ratios of the velocity of translation to the velocity of rotation, and assuming that systems of velocities could be fitted to pressure lines of the same shape, it is inferred that cases of traveling revolving fluid would be indicated by isobars similar to those which are classed meteorologically as belonging to small second-
regard to cyclones and anticyclones of middle P atitudes is
9
cate revolvin fluid, and, vice versa, t R at traveliii
m s are drawn showing the distribution of ve P ocity in
aries, or distortions of the isobars, generaU on the
are next considered which must exist if a c o l p n of rotating fluid is maintained and transported within a
current represented b the isobars of a great c clonic
That, the velocity of translation niust be the velocity corres onding with the se aratioii of the isobars of the
ing mass. (2) The column must probabl extend throughout the tropos here, otherwise it could not be “capped.” (3) The ve P ocity of the current transporting the revolving fluid must be the same at all heights. This condition is shown to be satisfied if the line of lapse of temperature with height in the atmosphere corresponds witah an adiabatic line, aiid this is known to be approxi- mately the case in a cyclonic depression where coiivec,tioii hits been uliquit oils ant1 vigorous.
southern side of the great cyolonic systems. d onditions
depression. The con B itions arrived at are brie jiy y: (1)
main s epression unaffectec f by the presence of the revolv-
MOTION OF A PARTICLE ON THE SURFACE OF A SMOOTH
ROTATING GLOBE.’
By F. J. W. WHIPPLE.
[Reprinlrd/rurn Science Abstracts. Sect. A, A L I ~. 30. 1917, $721.1
The free motion of a particle over a smooth rotating glob0 has not in the ast received much attention, but
such a particle will rove a useful pre iminary to a proper
mtuall occurs in winds, where the air particles have other
briefly dealing with the case of a article on a smooth rotating sphere, the case of a fo!e having a “level” surface is considered. During t e motion over the sur- face the relative speed remains constant. If the velocit is small so that variation in latitude is negligible the trac is a circle and the period of the motion relative to the surface of the globe 4 cosec 9 days (where 9 =latitude.) Where vsriatioiis of latitude inlist, be taken into account the general equations are worked out, hit before a com- plet,e solution c.an be found it is necessary to assume that 9 is small throughout the motion. The equations are
thus approximate only and must not be used for high latitudes. The solution then falls into 3 classes according as constant G is positive, zero, or negative. The value of C is governed by the initial motion and starting point
of the particle. The results are illust-rated by curves which show the niotioii of R pai.ticle given the velocity of 10 m./sec. over a globe having the dimensions of the earth. The first set of curves (0 positive) give oscillatory paths backward and forward across the equator. In tlie second set (C=O) after a looped path the particle approaches the equator asym totically. In the third case (C‘negative) motionis.con&ed to one side of tlie equator. An approxi- mately circular path is followed out, but with a gradual drift to tho westwartl.-J. B. L)i[~l.es].
fi:
the author considers t. f iat a knowled e of the motion of
understanding of t R e more complicated motion whch
forces t esides that of gravity acting upon them. After
I
MOTION OF THE AIR IN THE LOWEST LAYEBS OF THE ATYOSPRERE .z
By G. HELLMANN.
[XepriMldfrom Science Abstracts, Sect. A, Aug. 30,1917.D 732.3
From iiieasureiiients of the wind velocity at five dif- rerent heights up to 858 nieters above the ground at the
1 RepriWfrom Nature London July 5 1917 99378.
A b t m t published iithis REGIEW dug& 1917, pp. 413-414.4. A., Jr. ; Philosophlcal Mag London June 1917 33-457-471.
- Berichte, Preuss. zkad. Wi& B e h , i917; 10174-197.