REPORT OF COMMITTEE ON PUBLICATION 87 



These figures indicate that the minimum degree of ripeness, that neces- 

 sary for table grapes, requires about 1900 units of heat or about 400 more 

 than Angot's maximum in the case of Muscat at Fresno. The degree of ripe- 

 ness necessary for raisin-making similarly requires about 2300 units or 900 

 more. At Davis the figures approximate those of Angot more closely, being 

 about 1500 and 1700 respectively. This fortifies the conclusion already 

 reached by a different route that in warmer regions more heat is needed 

 than in cooler for the same results. Accepting the minimum degree of ripe- 

 ness as representing Angot's calculation, the 400 extra units needed at Fresno 

 represent almost exactly the heat of the month of August. Grapes which 

 should ripen according to the theory about August 1, actually ripen at Fresno 

 about September 1, or four weeks later. 



The seasonal sum of heat is sufficient in all the cases shown in Fig. I 

 with the exception of that of Eureka, even though we allow an increase of 

 time of three weeks over that required by Angot's theory. The figures, how- 

 ever, represent averages for a term of years and the variations between 

 different years are considerable. No locality is safe for planting, therefore, 

 where the average seasonal sum is close to the minimum. This is the case 

 of Berkeley, where even early grapes do not ripen every year. At Sissons, 

 near the northern border of California, the sum of heat is sufficient for early 

 varieties, but the possibility of the occurrence of frost even in July makes 

 grape growing uncertain. 



The temperature curve for Napa shows some of the causes of the super- 

 iority of the Coast ranges and valleys for the production of dry wine. The 

 development of the vine and its fruit there requires from seven to eight 

 months, as compared to the five or six months shown for Bakersfield at the 

 upper end of the San Joaquin Valley. This slow ripening results in a higher 

 acidity at maturity and brings the vintage to a time of year when the weather 

 is cool and favorable to proper fermentation. 



The temperature curves for Merced and Bakersfield show ideal climatic 

 conditions for the production of raisins. The sum of heat necessary for the 

 ripening of even late varieties, is obtained while there still remain several 

 weeks or hot, dry weather for the drying of the raisins. The temperature 

 conditions for Redding, at the upper end of the Sacramento Valley, are almost 

 identical with those of the corresponding part of the San Joaquin, but the 

 autumn rains are more abundant and occur about a month earlier. This 

 makes the drying of raisins precarious. 



Dry Summers. 



The black areas on the diagram indicate the annual rainfall for each 

 locality and its distribution by months. They show apparently that the con- 

 dition of a dry summer is fulfilled for all the California localities. The 

 absence of rain, however, is not all that is needed. The harm of summer 

 moisture is not due to the wetting of the soil. This may be an advantage and 

 is often brought about intentionally by means of irrigation. Harm results 

 only when the air is both warm and moist for considerable periods. Such a 

 condition is shown by the record for Raleigh, N. C., which shows that the 

 warmest month is also the wettest and that rain falls abundantly during 

 every month of the growing season. So much rain cannot fall without pro- 

 ducing excessive moisture in the air for considerable periods. It is this 



