62 MANUAL OF GARDENING 
very considerable undulations may be left in the surface with 
excellent effect. In lawns of this size, or even half this size, 
it is rarely advisable to have them perfectly flat and level. 
They should slope gradually away from the house; and when 
the lawn is seventy-five feet or more in width, it may be slightly 
crowning with good effect. A lawn should seldom be hollow, 
— that is, lower in the center than at the borders, — and broad 
lawns that are perfectly flat and level often appear to be hollow. 
A slope of one foot in twenty or thirty is none too much for a 
pleasant grade in lawns of some extent. 
In small places, the grading may be done by the eye, unless 
there are very particular conditions to meet. In large or 
difficult areas, it is well to have the place contoured by instru- 
ments. This is particularly desirable if the grading is to be 
done on contract. <A basal or datum line is established, above 
or below which all surfaces are to be shaped at measured 
distances. Even in small yards, such a datum line is desirable 
for the best kind of work. 
The terrace. 
In places in which the natural slope is very perceptible, there 
is a tendency to terrace the lawn for the purpose of making the 
various parts or sections of it more or less level and plane. 
In nearly all cases, however, a terrace in a main lawn is objec- 
tionable. It cuts the lawn into two or more portions, and 
thereby makes it look smaller and spoils the effect of the picture. 
A terrace always obtrudes a hard and rigid line, and fastens 
the attention upon itself rather than upon the landscape. Ter- 
races are also expensive to make and to keep in order; and a 
shabby terrace is always distracting. 
When formal effects are desired, their success depends, how- 
ever, very largely on the rigidity of the lines and the care with 
which they are maintained. If a terrace is necessary, it should 
be in the form of a retaining wall next the street, or else it 
