202 Forecasting Weather. 



"Other means of iirotection have been tried. Saturation with water of the 

 ground in which the plants are growing is resorted to in fruit plantations in 

 California. Possibly the evaporation of the water is in itself a protection, as it 

 promotes the formation of a mist over the land to be protected, but the 

 warmth of the water itself no doubt also acts to prevent the air just above it 

 being cooled as much as it would have been if the ground had been dry. On 

 the other hand Continental writers point out that delicate plants are more 

 sensitive to the effects of frost when their cells are fully charged with water 

 than when they are in a dry condition, and then the adoption of this method, 

 though mitigating the intensity of frost, may lead to increased damage to the 

 crop. Possibly differences in the character of the crops to be protected, more 

 particularly the heights of the sensitive parts above the ground, may account 

 for the apparent difference of opinion. On occasions when there is an 

 appreciable breeze saturation of the ground is probably harmful, as it would 

 promote increased evaporation, and so lead to cooling while the protecting mist 

 would be dispersed bj' the breeze as rapidly as it was formed. ' Smudging,' i.e. 

 covering the area with smoke from the combustion of damp straw or other 

 smoky fuels, has been recommended as a protective measure, and the experi- 

 ments have given rise to some discussion. 



"Vegetation suffers most when the plants are rapidly warmed by the sun 

 after being exposed to frost, so that protection is useful in the early morning 

 when the sun is rising." 



Dr. Shaw's remarks on the " Practical Utility of Weather 

 Forecasts " are also worthy of serious attention. He says : — 



"Any one receiving a telegraphic forecast for the first time hardly knows 

 what to do with it. He looks at the sky and ransacks his own experience ; if 

 his habitual prognostics support the forecast he will act upon it ; if they are in 

 conflict with it he can hardly trust himself to the inferences drawn from 

 premises unknown to him by persons who do not live out of doors or otherwise 

 share his experience. In the end he is almost sure to be guided by his own 

 experience, and then indulge in a judgment ex pout facto upon his wisdom 

 in having so determined. 



" The fact is that the effective use of telegraphic; forecasts requires practice, 

 anil it also requires co-ordination with the prognostics, general or local, wiWi 

 which the user is familiar. Supposing that we could re-arrange the practice of 

 forecasting so as to give in the evening the weather anticipated for the period 

 6 a.m. next morning to 6 a.m. on the following morning, and in the morning 

 the weather from the approaching midnight to midnight next evening, or even 

 from 6 p.m. to 6 p.m. ; and if the percentage of accuracy could be kept up to 

 its present figure, there is no doubt that the recipient who always acted ujiim 

 the forecasts would find them, on the average, of effective utility, and the utility 

 could be very greatly enhanced by the consideration daj' by day by some 

 person of special knowledge on the spot of the relation of the forecasts to 

 actuality, the reasons for success and failure, and the preliminary signs of the 

 commencement and sequence of the changes anticipated. This development 

 requires a local knf)wledge of the principles of forecasting by means of weather 

 charts, which might form part of a rural education. A well-informed corres- 

 pondent in possession of the general inferences could proliably give a local 

 forecast that would be lietter apjilicable to the particular district than the 

 general official forecast. 



" Until such a development is possible we cannot be said to have a ' .system ' 

 of forecasting, and a judgment as to the utility of our forecast practice gives 

 no adequate information up<in the progress of the sul)ject from the scientific 

 ])oint of view. 



•■ .\fter wiiat I liave said it is not surprising that tlic rciijiis which \vr irrt 

 about tlie application of forecasts deal more with their accuracy than with 

 their utility. Correspondents who receive the liarvcst forecast by telegram. 



