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 



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. 



