April 28, 1899.] 



SCIENCE. 



627 



CURRENT NOTES ON METEOROLOGY. 

 FROST PREDICTION AND PROTECTION. 



Bulletin No. 23 of the Weather Bureau is 

 entitled Frost : When to Expect it and Eoiu to 

 Lessen the Injury Therefrom, and is by Professor 

 W. H. Hammon, Local Forecast Official at San 

 Francisco. This paper is a revision of one pre- 

 pared three years ago, and is the result of care- 

 ful study extending over a long period. The 

 Bulletin classifies the different methods of frost 

 protection under five heads. Of these the most 

 important ones are as follows : I., diminishing 

 radiation ; II., raising the dew point of the air, 

 and, III., increasing the temperature of the air. 

 Under the first class come screens of various 

 kinds, such as glass, cloth or laths ; and the 

 well-known 'smudges.' The raising of the 

 dew point is accomplished by burning damp 

 ' smudges ; ' by evaporation from water tanks 

 heated by fires ; by spraying and by irrigating 

 at times of frost, etc. The heating of the air by 

 means of small fires, scattered about through 

 the orchard or over the field, has also been 

 found a very effective protector against frost in 

 the drier parts of California. Among the vari- 

 ous ingenious devices cited by Professor Ham- 

 mon, the following is worthy of note. The ma- 

 chine, designed by Mr. George F. Ditzler, of 

 Biggs, Cal., consists of a large, deep, sheet iron 

 tank, three or four feet square, mounted on a 

 truck. About six inches from the bottom of the 

 tank a wire grate is erected. Through a 

 hole in the bottom of the tank, beneath 

 the screen, a blast of air is admitted, 

 which is produced by a revolving fan, 

 operated by a sprocket chain and wheel at- 

 tached to the wheel of the truck. A water 

 cask and force pump, operated by the move- 

 ment of the wagon, complete the outfit. A 

 little tar or other fuel is placed upon the grate 

 and ignited, and the tank is filled with wet 

 straw or manure. When the machine is put 

 in motion the blast produced by the fan causes 

 an intense fire. All the heat of the fire has to 

 pass through three feet of wet straw before it 

 can reach the air. Thus evaporation is very 

 active, and the vapor, rising from the wet ma- 

 terial, immediately condenses, forming a dense 

 fog or mist. AVhile the machine is in motion, 

 being driven forward and back between the 



rows of trees in the orchard, water is continu 

 ally pumped from the cask and discharged 

 from small holes about the top of the tank upon 

 the fuel. One such machine is said to evapo- 

 rate 100 gallons of water an hour. The fog 

 thus formed is stated to be so dense that the 

 driver has frequently to go ahead and lead the 

 horses. 



A FOG DISPELLER. 



While the production of fog, as a means of 

 protection against frost, is an extremely desi- 

 rable thing in some districts on land, the pos- 

 sibility of dispelling fog over the oceans is an- 

 other matter which is no less anxiously sought 

 for. The following account of the so-called 

 Tugrin Fog Dispeller is found in the Monthly 

 Weather Review for January. The apparatus 

 consists of an outlook pipe, eight feet long and 

 three inches inside diameter, with a wide flange 

 at the mouth, placed so as to be convenient to 

 the navigating officer. A tube enters the pipe 

 from below, and a blower sends a powerful 

 stream of warm air through the tube and the 

 pipe straight ahead, blowing a hole right 

 through the fog, which is rolled back in every 

 direction. It is said that the navigating officer 

 is thus enabled to see through the densest fog 

 for several hundred feet. 



NOTES. 



The report of the Meteorological Council to 

 the Royal Society for the year ending March 

 31, 1898, shows that of the 8:30 p. m. forecasts 

 issued daily the percentage of verification was 

 81. Fifty-five per cent, of these forecasts were 

 fully verified, and 26 per cent, were partly 

 verified. The highest percentage of verification 

 attained during the decade 1888-1897 was 84, 

 in 1893. Of the storm warnings issued during 

 the past year, 91.8 per cent, were justified by 

 subsequent gales or strong winds. 



The progress of the investigation of the free 

 air by means of kites continues. From the 

 Monthly Weather Bevieiv for January it is learned 

 that a kite corps has been formed at Bayonne, 

 N. J., and that nearly 40 ascents were made be- 

 tween April and December of last year. The 

 altitudes reached were in most cases not above 

 500 feet, and observations of temperature only 

 were made. K. DeC. Ward. 



Harvard University. 



