Popular Science Monthly 



595 



Telling the Age of Water-Marks 

 On a Lake Shore 



A RECENT investigation of the water 

 level of lakes by two consulting en- 

 gineers, one an American and the other a 

 Canadian, resulted in the collection of 

 interesting data on the age of water-marks 

 and stains on the rocks along a lake shore. 

 Moss and lichens, common vegetation in 

 northern latitudes, 

 play an important 

 part in this study, 

 the water stains on 

 the rock being due 

 to the absence or 

 partial absence of 

 one or more forms of 

 these, lichens. The 

 removal of these li- 

 chens and the form- 

 ation of a mark by 

 standing water ma}- 

 occur in a com- 

 paratively short 

 time, possibly in a 

 season, but a num- 

 ber of years are re- 

 quired to change 

 substantially the 

 sharpness of a water 

 line once formed. 



One of the accom- 

 panying illustrations 

 showsclearly the ap- 

 pearance of these 

 stains or water- 

 marks. It may be 

 noticed that the 

 marks are higher on 

 the exposed face of 

 the rock than around 

 the corner where the 

 rock is protected to 

 some extent from 

 wave action. The 

 other illustration 

 suggests the length 

 alter a mark 



of time required to 

 On this rock a high-water 

 mark was cut in 1895 at the point indicated 

 by the pencil. It is still plainly visible 

 and practically unaltered, although it is 

 no longer the high-water mark for that 

 particular locality. 



One of the most interesting series of 

 water-marks left by large inland bodies of 

 water may be seen on rocks which now He 

 far above the level of Great Salt Lake. 

 These rocks tell the story of the lake's 

 'gradual evaporation. 



Replacing Rags with Waste Tanbark 

 in Making Coarse Paper 



TO-DAY the price of plain everyday rags 

 is soaring high above the clouds in 

 company with thatof most commodities. Its 

 use in the manufacture of paper has there- 

 fore greatly diminished. Not that we are 

 making less paper than before, but because 

 a cheaper substitute has been found for 

 the rags. This 

 substitute is waste 

 tanbark. In the 

 manufacture of wall- 

 paper alone fully 

 eighty per cent of 

 the rags previously 

 used are being suc- 

 cessfully replaced by 

 it. 



The greatest total 

 saving that tanbark 

 is effecting, how- 

 ever, is in the pro- 

 duction of felt shin- 

 gles for roofing. The 

 United States has 

 been manufacturing 

 nearly nine million 

 square feet of these 

 shingles each year. 

 The material enter- 

 ing into them weighs 

 about two hundred 

 and forty thousand 

 tons. Of this, by 

 far the greatest part 

 has been made of 

 rags. But now 



over thirty per cent 

 of this is being re- 

 placed by the tan- 

 bark, and the fin- 

 ished product is as 

 satisfactory as it 

 ever was. 



The tanbark is 

 made up of the bark of oak and hemlock 

 trees. Some seven hundred thousand tons 

 of it had been going to waste each year. 

 But now, after the valuable tannin has been 

 extracted from the waste, every scrap of it 

 is being put to this new usage. Even the 

 worn-out tanbark flooring used in riding 

 academies and for exhibition purposes may 

 be used again in this way. 



It would seem then that felt shingles for 

 roofing would be one of the few manufac- 

 tured articles the price of which has not 

 been augmented by the war. 



On the rock shown in the illustration at the 

 top a high-water mark was cut in 1895. In 

 the oval appear water-marks and stains 



