316 TRANSACTIONS OF THE HORnCULTURAL 



These conclusions are of the greatest importance, and the 

 practical grape grower will, doubtless, have no difficulty in finding 

 means for their application. Some of us remember the story told 

 of the vineyardist of the South of France, whose vineyard was lit- 

 erally covered with stones. To improve the appearance of the vine- 

 yarn he removed the stones. His crop dwindled and declined until 

 finally he returned the stones to their accustomed places and the 

 wonted fruitfulness returned. 



But while these general considerations show the influence of 

 light upon the vine, the exact determination of the relation between 

 the quantity of light falling upon the vine, and the quantity of 

 work effected within the leaves, is a problem of greater difiiculty, 

 and it is only within the past decade that means have been devised 

 by which it is possible, with any degree of accuracy, to arrive at 

 numerical results. In former years meteorologists depended entirely 

 upon the percentage of cloudiness to express the amount of light 

 reaching the earth and acting with favorable effect upon vegetation. 

 But the results thus obtained were very unsatisfactory. What won- 

 der then if the scientific or practical agriculturists were unable to 

 deduce from them any conclusions of value bearing upon the de- 

 velopment and maturity of crops. Relations were sought for in 

 vain, and attempts at the application of these results always proved 

 •entirely futile, and it was left to the fertile mind of the greatest of 

 meteorologists, Marie-Davy, Director of the Montsouris Observatory, 

 near Paris, to devise means for solving this great difficulty in agri- 

 cultural meteorology. His actinometer, or solar radiator thermom- 

 eter, fulfils all the demands of the practical farmer or fruit grower, 

 and it is to be hoped that before long it will be very extensively 

 used. This instrument consists of a thermometer with blackened 

 bulb, the whole enclosed within a tube, from which all air has been 

 exhausted. Its construction is based upon the fact that direct light 

 from the sun is always accompanied by radiated heat, and that both 

 may be diminished by very nearly the same causes, such as interven- 

 tion of a cloud, mist, fog, etc., and therefore the difference between 

 the indications of this instrument and those of a thermometer with 

 a bright bulb and representing radiated heat must also represent di- 

 rect light. 



Both Marie-Davy in France and Levy in Austria have fully 

 established the value of the observations made with this instrument, 

 and they have invariably found that a higher proportion of those 

 constituents of the grape most favorable to the production of good 

 wine always accompanies a series of high indications with this in- 

 strument, provided, of course, a proper general temperature pre- 

 vails. We need not enter into the details of these very careful ob- 

 servations that have been carried on now for a number of years, but 

 it is sufficient to say that the results are such that every station for 

 observations in agricultural, or at least horticultural, meteorology, 



