34 MANUAL OF AMERICAN GRAPE-GROWING 



freezing ceases, for the reason that the atmosphere is rarer and 

 drier so that heat radiates rapidly from the land. As the 

 height increases, also, the revels of the wind play havoc with 

 the vines. Yet, one is often surprised to find good vineyards 

 at the level of the lakes or, on the other hand, crowning high 

 hills. Altitude in grape-growing must, therefore, be deter- 

 mined by experiment. We know very little of the formation 

 of the thermal belts on high land so favorable to the grape. 



The lay of the land. 



We associate the grape with rugged land ; as the vines on 

 the banks of the Rhine, the rolling lands of Burgundy, the 

 slopes of Vesuvius and Olympus, the high hills of ^Madeira, the 

 cloud-capped mountains of Teneriffe, mountain slopes in 

 California and the escarpments of grape regions in eastern 

 America. These examples prove how well adapted rolling 

 lands, inclined plains and even steep and rocky hillsides are to 

 the culture of the vine. Virgil long ago wrote, "Bacchus is 

 partial to broad, sunny hills." Yet rolling lands are not es- 

 sential to the culture of the grape, for in Europe and America 

 very good gra])es are grown on unsheltered plains, provided 

 the land has an elevation on one or more boundaries above the 

 surrounding country. If the conditions of soil and climate 

 which the grape requires can be found on level land or moder- 

 ate slopes, such situations are much better than steep decliv- 

 ities, since on these the cost of all vineyard operations is greater 

 and heavy rains erode the soil. The soil on hills, too, is often 

 scant and niggardly. Level land, however, must not be shut 

 in on all sides by higher land as untimely frost will often 

 lay waste vines in such a situation. 



Exposures. 



The exposure, or the slope of the land toward a point of the 

 compass, is important in choosing a site for the vineyard, al- 



