107 
p. 2385.) He finds that with the temperature of the air 84° F. and a 
relative humidity 50 per cent the evaporation varies with the velocity 
of the wind at the surface of the moist disk as in the following para- 
graph: 
INFLUENCE OF THE WIND ON EVAPORATION, 
At 5 miles an hour the evaporation is 2.2 times that in a calm; at 10 
miles, 3.8 times; at 15 miles, 4.9 times; at 20 miles, 5.7 times; at 25 
miles, 6.1 times; at 30 miles, 6.3 times. 
The observations of the Piche instruments, as exposed in Signal 
Service shelters at 18 different stations, gave the results in the table 
following. (See Monthly Weather Review, September, 1888, p. 236.) 
The readings on the scale of the Piche instrument have been con- 
verted into depths of water that would be evaporated from a free 
surface of water within the same instrument shelter during the 
respective months by multiplying them by the constant coefficient 
1.33, so that the evaporations here given in inches of depth of water 
correspond entirely to the ordinary methods of measuring rainfall. 
Evaporation, in inches, observed with Piche instruments within the Signal Service 
thermometer shelters in 1888. 
Station. June. July. | August. | Rep lent: 
| ; 
| Inches. | Inches. | Inches. | Inches. 
FES OTe eee ed see ose mes Moma Ty ate | 5.16} 5.87 5.28 | 2.68 
WGN? ADF Ee Se ea SS SO ae PR = Fa ane Ae pe ee 4.49 5. 36 4,14 2.88 
IVES IT GOT as ee manne tee eed SAAS SERS CIOS ASL ee | 4. 64. | 5.27 4.22 | 2.52 
Buffalo -__... byt sep nc ipes net B14 Nason ae eS ieee boat Pikyen aia 3.70 
Cincinnati ______ LACIE Ae Cp SOUR EY PRN ere oo | 6.22 6.93 5. 36 5.33 
Wi Rep rey SVU) = SOS NS A SR lel Ue hk ee | 53s 5. 24 4.57 3.86 
ING waOrloanses sot es le nas ee ees se) AES BLM EREE 3. 82 9.38 7.96 3.70 
(CHICHE ORRE nee een ee eae. ect Comoe nell yee kde 5.59 5. 52 6. 97 5.79 
SU WINOUIS Beet N= Gare ees oe eee coos nent eee ne else 6.18 5.79 4.41 4.61 
Ee COT ea agg en ge lh ANE | 11.66] 12.76] 12.69 10.95 
ST ES Ae NG Sg HR Ee OR | 13. 86 13. 63 12.88 10.36 
IDI ER SY 2 3 eel nae eae ee ays See sae ee Me eae | 13.91 9.89 11.54 10.00 
DOG Pel City eee eee re ee ee ee ae ee Se ee 7.80 8.20 6. 22 6.07 
SEAT LONI O seer e essen mee met Mere ean eran cee eee nee te 2.7 5.08 5. 36 3.66 
brett mat seh as WE NAD) “ey Pt heey Che ee ehetiy! 6. 62 5.44 6.78 
NS) STV Tas a en a re ee ee abn es 9. 42 10. 91 8.55 5. 94 
SCRA COM Seine se a eee Aon ie Se Se ees SS 5.63 4.33 DY 9% | Eoote eee es 
elena see same ose Soe ye eta oat ee ete eee enna se awdce ae 4,88 8.20 7.80 6. 86 
IBOISCL Clty aece eee ate neeeee ow Secs tie Pe i eS vee 5.83 9.14 7.68 (a) 
“In October at Boise City the evaporation was 7.60 inches. 
Profesor Russell has also devised the following very satisfactory 
formula connecting the total daily evaporation in inches with the 
meteorological elements on which it depends, viz, the vapor tensions, 
Pw for mean wet bulb and pa for mean dew-point temperatures, (0) 
barometric pressure, by means of which he has been able to compute 
