The ornamental design for a thermometer, as shown and described.
FIG. 1 is a top, front, right side perspective view;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The article is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.
In the drawings, the broken lines are for the purpose of illustrating environment only, and form no part of the claimed design.