TESTING GRAPE VARIETIES IN" THE VINIFERA REGIONS. 
gravelly clay loam or heavy loam, containing a large quantity of 
organic matter formed in a swamp or lagoon extending in past geo- 
logical ages up Napa Valley from San Pablo Bay, typical of the greater 
part of the soils in the valley floor. On weathering, the shales, sand- 
stones, limestones, lime conglomerates, and large quantities of usually 
lenticular or angular gravel with little erosion of edges are washed 
down from the steep hills or mountains surrounding Napa Valley on 
COUNT/ ES INDICATED ON MAP 
Br NUMERALS AS EOLLOtVS 
/*? COUNTY 
Fig. 1.— Map of California, showing (by large black dots) the location of the twelve experiment vine- 
yards of the Bureau of Plant Industry. 
all sides except the south, and tend to form a heavy or clayey soil with 
only small quantities of sand. No hardpan or alkali appears. The 
surface is undulating, affording a fairly rapid run-off of surplus rain- 
water, though in places the subsoil is quite wet during the spring 
months. No irrigation is necessary. The clay and silt in the sub- 
soils greatly aid in retaining moisture in spite of the large quantity of 
