258 



Popular Science Monthly 



How to Sit Straight and Still be 

 Comfortable 



THE ordinary straight-back chair 

 encourages incorrect posture. It 

 does not conform to the natural mould 

 of the back. The sitter must assume a 

 slouching attitude to be comfortable. 



The cushion fits into the small of the 

 sitter's back and encourages him to sit 

 upright with the chest properly raised 



All this is remedied by a simple de- 

 vice invented by Dr. J. H. Kellogg of 

 Battle Creek, Michigan. The device is 

 a small leather or cloth bound cushion 

 which may be attached to any chair. 

 This cushion is so placed that it fits into 

 the small of the sitter's back and en- 

 ables him to sit upright, with chest 

 properly raised and at the same time to 

 be comfortable. 



Concrete to Replace Willow Mats 



EXPERIMENTS have been made by 

 the United States Bureau of Stand- 

 ards to develop a method for accelerat- 

 ing the hardening of concrete in order 

 that concrete may be substituted for the 

 willow mats that have been used in the 

 past along the Mississippi River. As a 

 result of the experiment, it was found 

 that four per cent of calcium chloride 

 added to the mixing water increases the 

 strength of the one-day-old concrete one 

 hundred per cent. 



Testing a Hack- Saw's Strength 



IX order to prove that a hack saw is 

 an instrument of remarkable tensile 

 strength, an experiment was recently con- 

 ducted at Springfield, Mass. It was 

 found that the thin steel would sustain 

 without injury two hundred and eighty- 

 two pounds, the weight of two men. 



Much damage is done to hack saws by 

 too speedy operation, the operator often 

 forgetting that it is the action, not the 

 speed, that does the work. A hack saw 

 should not be run faster than forty to 

 sixty strokes a minute, and no blade 

 will stand a higher speed without injury. 



The thin hack-saw, although bending 



badly, is supporting two hundred and 



eighty-two pounds without damage to 



itself 



