Bourdon, Tait, and Amagat High-Pressure Gauges. 401 



oil mentioned in rny last paper*, the manometre could, be at 

 once connected with the screw-compressor. I also floated 

 the lower piston in this oil. Thus the same oily liquid is used 

 for the transmission of pressure, with advantage, I think, 

 throughout the system of apparatus. 



3. The Bourdon Gauge. — The gauge used was the same to 

 which my earlier measurements apply, having a tube of steel 

 or ironf. I made two series of comparison of this gauge 

 with the manometre. In the first of these, the usual multiply- 

 ing gear was used ; in the other the excursions of the free 

 end of the Bourdon tube were read off directly with a Fraun- 

 hofer microscopic micrometer, after the multiplying gear had 

 been removed. Tables I. and II. contain examples of the 

 measurements made. There are four series of observations, 

 two of them within an interval of 500 atmospheres, the other 

 two within 1000 atmospheres. In both cases two values are 

 shown for each stop of pressure. Table II. gives the micro- 

 meter position of the free end of the Bourdon tube prolonged, 

 in centim. /40, this being the scale part of the micrometer. 

 As usual, the observations were made in triplets, two at the 

 manometre, including each one at the Bourdon gauge. 



Table I. — Cyclic Comparisons of the Bourdon Gauge 

 (multiplying gear) with the Amagat Manometre. 



Bourdon 



Atm. 



*1SS 

 174 

 322 

 312 

 457 

 446 

 316 

 313 

 1G2 

 165 

 27 



Ainagat. 



Atm. 



*185 

 173 

 325 

 314 

 459 

 448 

 314 

 311 

 157 

 158 

 23 



**29 

 172 

 168 

 317 

 305 

 462 



**24 

 170 

 165 

 318 j 

 306 

 464 



Bourdon. Amagat 



Atm. 

 444 

 433 



224 

 225 



83 

 84 

 20 



Atm. 



447 



435 



219 



221 



78 



78 



16 



121 

 •242 

 231 

 472 

 457 

 660 

 640 

 859 

 844 



no 



241 

 232 

 474 

 461 

 660 

 642 

 849 

 833 



Bourdon. 



Atm. 

 991 

 977 

 847 

 837 

 651 

 646 

 475 

 475 

 262 

 263 

 28 



Amagat. 



Atm. 

 982 

 962 

 815 

 804 

 606 

 601 

 421 

 420 

 223 

 225 

 16 



|30 



|19 



251 



250 



245 



243 



465 



468 



458 



458 



Bourdon. 



Amagat. 



Atm. 



Atm. 



650 



653 



645 



647 



855 



860 



838 



832 



985 



982 



977 



960 



964 



954 



950 



937 



840 



809 



834 



802 



631 



587 



626 



5S2 



440 



386 



440 



386 



260 



215 



264 



222 



35 



23 



First 



** Second series. t Third series. 



* This Magazine, [5] xxxi. p. 10 (1891). 



t Probably of iron; unfortunately I cannot tell which without ana- 

 lysing the tube or breaking it. 



Phil. Mag. S. 5. Vol. 31. No. 192. May 1891. 2 G 



