Popular Science Monthly 



8G7 



"This part of the dam has only recently 

 been laid," said the engineer, "and the 

 heat, generated chemically b\- the cement 

 in the concrete as it solidified, has not 

 passed off yet." 



Then he explained that concrete expands 

 and contracts, after the fashion of steel, 

 and that the dam had been built in sections 

 about seventy-nine feet long, interlocking 

 from the bottom to the top. Observation 

 of other Cyclopean structures of masonrj- 

 had revealed the fact that in the course of 

 expansion and contraction cracks appeared 

 about se\"enty-ninc feet apart. So it had 

 been decided to provide in this way for 

 expansion-joints in the dam. 



As little was known of the changes of 

 temperature which occurred in a large 

 mass of concrete and as this information 

 might be of value in designing other 

 structures of similar character, it was 

 determined when the Kensico dam was 

 built that its temperature should be taken 

 regularly at different points between the 

 base which is one hundred and fifty feet 

 below the surface of the ground and the 

 top, approximately the same distance 

 above it. This has now been done 

 for a period of more than two years, , 



an electric thermometer being used /^i': 

 for the purpo.'ic. 



A thermophone is a de\ice 

 which will measure by means of 

 an electric circuit the tempera- 

 ture at any point connected 

 with it by wires. Its principle is 

 that of the well-known Wheat- 

 stone bridge by which resist - 



ancescanbemeasured.Thecablc which leads 

 from the recording apparatus and the dry 

 batteries to the sensitive resistance coils 

 where the temperature is to be taken carries 

 three insulated wires. Through one of them 

 the current passes to the sensitive terminal, 

 where it is divided and returned through 

 two minute coils of copper and German 

 silver wire. These metals are affected 

 differently by changes in temperature. 

 These changes affect differently the free- 

 dom with which a current of electricity will 

 pass through them, and this difference in- 

 dicate what the temi)erature is. 



Forty-seven thermometers were buried in 

 the dam, the lowest being below the founda- 

 tion. They were connected with switch- 

 boards placed at central points, the cables, 

 carefully protected, being buried in the 

 masonry as it rose. There are three switch- 

 boards, the lowest being stationed in a 

 nook in the long inspection-galler)\ 



I 



-flK^ 



Will the Great Sphinx Scowl 

 When She Sees This? 

 X seeing America first one should not 

 ■ ivcrlnok the Sphinx built at Blue Point, 

 Long Island, by William 

 Graharq. This domestic 

 Sphinx is just one seventh the 

 size of the original great 

 Sphinx in Egypt, and it 

 !s just as mute. It 

 weighs forty-two tons. 



The idea of decorating 

 his Iront yard with a copy 

 of Egypt's great at- 

 traction came to Mr. 

 Graham when he was 

 renuning a large 

 quantity of sand 

 from his lawn. In- 

 stead of carting 

 the sand away, as 

 he had done in 

 past years, he col- 

 lected it in a huge 

 pile, and then 

 drew up plans for 

 his Sphinx. The 

 sand was mixed 

 ^\ ith concrete and 

 iron scrap. 

 The head of Mr. Graham's 

 jfi Sphinx is solid, weighing ten tons. 

 ^^~*i* The lower part of the image has 

 a circular chamber with an open- 

 ing at the rear. Seats and pillars of concrete 

 extend around its inner walls. 



The head of the Sphinx 

 weighs ten tons. The 

 lower part of the image 

 is a room with an 

 opening at the rear 



