Popular Science Monthb/ 



31 



"Ironing Out" Earthquake 

 Wrinkles in San Francisco 



AT the liim- of the earth- 

 (jiiake many pavements 

 of San Francisco "wrinkled" 

 under the strain. Traffic 

 since has increased tlie iine\en 

 surface. By the use of the 

 machine shown in the picture, 

 old pavements are made like 

 new. A traction -engine is 

 fitted with an oil-blast furnace 

 and a hood by which a section 

 of pavement from the curb to 

 the car track is softened until 

 it can be leveled by raking. 

 Each section is then success! \elysniui )t lied 

 and rolled in the regulation way. 



The most disastrous efifects of the 

 earthciuake occurred in parts of the city 

 where the ground consisted of "made" 

 land, especially in a large area adjoining 

 the Bay, which consisted originally of 

 mud flats and overflowed lands built up 

 with layers of sand, waste, and the like. 

 Under the shaking of the eartii<iuake, 

 this soft ground tended to flow along 

 the slopes, causing pavements and street- 

 car tracks to break up or buckle. Here 

 and there the ground was rolled into 

 waves three or four feet high. Where 

 the texture of the soil was very loose, 

 the ground surface was lowered. What 

 occurred in the latter case was just what 

 happens when a measure into which 



Intense heat from an oil-blast furnace is applied to 

 breaks in the pavement so that it can be leveled 



gr.iin or loose sand has been pcjurcd is 

 shaken in order to make it settle down. 

 The shaking causes the particles to come 

 closer together and the mass occupies 

 less space. The rainfall had been much 

 above the normal for three months before 

 the earthquake, and the soil was there- 

 fore more soft and plastic than usual. 



Many observers in the region visited 

 by this memorable earthquake have 

 furnished graphic descriptions of the 

 visible undulations of the ground that 

 formed a feature of it, especially in 

 soft alluvial soils. The waves were from 

 one to three feet in height, and their 

 length, according to one description, was 

 about sixty feet from crest to crest. Trees 

 and telegraph-poles were seen to rise and 

 fall as the billows of earth swept by. 



w 



How Automobiles Innocently Break Windows 

 HEN a heavy autouKjbilc runs over pebble may be caught just right by the 

 pebbles no larger than a pea, a edge of the wheel and shot with such a 



high velocity that a broken 

 window is the result. One 

 firm in New York has had 

 three windows broken, all 

 in the same frame. The lay- 

 out at this particular place is 

 as indicated in the drawing. 

 The principle in\olved 

 is the same as that prac- 

 ticed in "shooting cherry 

 stones" by pinching the 

 slippery stones lietween the 

 lingers. In this case, though, 

 nuich higher velocities are 

 attained because oi the enor- 

 The heavy wheel of a motortruck shoots pebbles that mous loads nOW being placed 



break unprotected windows On trucks. 



