# Page:Popular Science Monthly Volume 90.djvu/300

284

��Popular Science Monthly

��Cost

��What Do Your Tires You a Mile?

A CHART for calculating the cost per mile per tire of an automobile has been circulated by a manufacturer of

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��A chart by means of which you may quick- ly find the actual cost of a tire per mile

automobile tires. Given the cost of the tire and the number of miles it is used, a pencil and a ruler will determine the exact cost of a "tire mile" in an instant. Con- sulting the chart which is reproduced here- with, we will suppose, as an example, that a tire cost \$15 and was used 2,500 miles before it wore out. The ruler is laid from the \$15 mark to the 2,500 mile mark and the line A — A drawn. Where the pencil line intersects the central vertical line, the precise cost of the tire per mile is shown.

��House Plants and How to Care for Them

THROUGHOUT the winter months flower lovers must depend on window- box gardens, unless they possess green- houses. A satisfactory and attractive window-box may be made as follows : Take a box about 8 in. deep and cover the bottom of it with stones or broken pottery for drainage. On top of this place a layer of moss to prevent the soil from working

��down and clogging the openings betweer the stones. The stones and moss together should take up about 2 in. of the depth ol the box. Fill in the remainder with soil to within 13^2 in- of the top.

The length of such a box depends on the width of the window. Its upper surface should be level with the window-sill. The supports may be brackets, a table, or legs permanently fastened to the box. To allow for more complete drainage, bore holes in the bottom of the box and place a drip pan beneath it.

The watering of the plants will depend

on weather conditions. On cloudy days in

winter about once a week will be

sufficient, while during the early

spring months watering may be

necessary every day. But even then

the top of the soil should be allowed to

dry occasionally. It is better to water

lightly and frequently than heavily and

at longer intervals.

The kinds of plants that will grow readily are begonias, ferns^ geraniums, Kenilworth ivy, smi- lax and aspidistra. The latter plant will thrive even though neglected, and direct sunlight is not essen- tial for it.

In addition to those mentioned for the window-box, palms, rubber plants and cacti may be grown in pots. The regular potting soil should be used, which consists of I part compost, i part good loam and I part sand. Although not essential, it is well to add 1/20 part of bone meal.

A potted plant must be examined from time to time to see if it needs a larger pot. This is done by inverting the plant when the soil is moist and tapping the pot until the soil and plant can be lifted out of the pot. If the ball of earth is entirely covered with roots it should be placed in a larger pot and new soil tamped firmly into the space around the ball.

To force the blossoming of geraniums indoors during the winter, the root growth should be restricted and the plants kept fairly dry. A potted fern must be kept moist all the time, but it must not be over- watered. Ferns should be given a bath occasionally by placing them in a tub and using weak suds made from a mild soap. All dust accumulation as well as minute insect parasites will thus be removed from the fronds. The suds should be rinsed off immediately. Palms should be watered regularly, but should not be kept moist.

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