Rule 1a. _A primary mass must be either vertical or horizontal according to the intended service, unless prohibited by technical requirements._ Service is an important factor inasmuch as it limits the intended use of the mass. A mass is horizontal when its largest dimension is horizontal. When the horizontal dimension of this mass is reduced until the main vertical dimension is longer than the main horizontal one, it becomes a vertical mass. As an example, a davenport is generally a horizontal mass intended to hold a number of people. When the mass is narrowed to the point where the vertical dimension exceeds the horizontal, it becomes a chair for one person. A low bowl may be intended for pansies, but as soon as the service changes and we design it for goldenrod, it becomes a vertical mass. The fable of the fox who, upon being invited to dine with the stork, found the tall vases unfitted for his use illustrates the change of mass with the change of service.
[Illustration: ANALYSIS OF THE PRIMARY MASS
[Sidenote: Horizontal and Vertical Primary Masses]
Figures 1 and 4, Plate 4, are examples of horizontal masses with the dark lines indicating the dominance of the horizontal lines and planes. The shelter house contains a long bench, making necessary the long horizontal lines of the building. The calendar holder has to be a horizontal mass because of the restrictions imposed by the shape of the calendar pad.
Figures 2 and 3 are vertical masses. The vase is intended for tall flowers, while the chair, as has already been mentioned, must meet the needs of a single person. Utility and service then have been found to give the primary mass a given direction or dominance.
The designer now represents this mass by drawing a rectangle similar to the block outline of Figure B, Plate 2. It is now necessary to see if the foundation stones of this rectangle have been laid correctly; in other words, to test the proportions of the primary vertical or horizontal mass.
[Sidenote: Proportions of the Primary Masses]
Rule 1b. _A primary mass should have the ratio of one to three, three to four, three to five, five to eight, seven to ten, or some similar proportion difficult for the eye to detect readily and analyze._ Proportions are generally expressed in terms of ratios. A surface of five by eight inches would give a ratio of five to eight; ten by sixteen feet is reducible to the same ratio. Certain ratios are monotonous and offend the eye by their lack of variety. Ratios such as one to one or one to two are of this class and should be avoided. If these ratios could speak they would resemble people talking in a low monotonous tone of voice.