Page:Popular Science Monthly Volume 91.djvu/747

 Popular Science Monthly

��731

��Eliminating the Periscope from the Submarine

THE terror of the German U-boats may be increased greatly since they have been constructed without peri- scopes. The sighting of the periscopes has saved many ships from destruc- tion. Without a periscope the sub- marine may approach unseen. The new German submarines are built with two lenses, one on either side of the boat, co-acting with other lenses and reflectors. The disadvantage of this method of constructing submarines is that the boat must be much nearer the surface of the water than it would have to be with a periscope.

��A Medical Battery No Bigger Than an Ordinary Flashlight

MOST medical batteries are as large as small-size suitcases and are therefore difficult to carry about. The battery illus- trated is no bigger than a flashlight, yet it gives sufficient current to afford a shock and operate the vibrator. A miniature battery is provided in one of the han- dles or containers, and in the other are carried the switch, the starter, the pin which regu- lates the current and the vibrator.

This type of battery will be found useful for mas- sage and wherever slight electrical stimulation is re- quired.

It takes up very little space in the physician's hand-bag; or it can be car- ried in the pocket without inconvenience.

���The pollen of the orchid is blown against the wires, and is held there and nourished by the dust

Orchids That Grow on Telegraph Wires Over the Streets

IN Porto Rico it is not unusual to have an orchid garden hanging over your house, suspended from telegraph wires. So heavy do the wires become when supporting the plants that it frequently becomes necessary for the telegraph companies to have them scraped to remove the growth. Tropical orchids usually cling to the trunks or branches of large trees or ferns, where they produce aerial roots which absorb moisture from the atmosphere. Some are climbers and others grow head downwards. One very beautiful species grows in moss. The one thing necessary for them is abundance of air. The plants shown in the pho- tograph above are evidently satisfied with their supply.

��Vibrator control

��chfor

����Spong

��The miniature battery gives sufficient cur- rent to operate the vibrator

��Details of the battery showing the complete- ness of its equip- ment for medi- cal purposes

��Regulating switch

��Why Anthracite Coal Lands Differ in Price

THE prices of anthracite coal lands vary from $200 to $1,000 an acre, the smallervalues being for lands containing rela- tively thin coal or practically exhausted veins. The medium values are paid for relatively small, unopened areas. The ex- treme values are for going con- cerns or for lands so located strategically that they have a special value for the purchaser.

�� �