abstracts: geodesy 73 



by atmospheric conditions, but when the proper corrections are made 

 a given lamp will repeat its value very closely. 



It is found that the pentane commercially obtainable increases in 

 density rather rapidly by the fractional distillation which occurs in the 

 lamp. The density (at 15°C.) should be between 0.6235 and 0.626, but 

 it usually reaches 0.635 when a little over half of the liquid has been 

 used. Beyond this point there is a marked increase in the intensity of 

 the flame. For an approximate correction, the variation may be as- 

 sumed to be linear and to be 1 per cent in candle power for each 0.01 in 

 the density of the liquid. 



When the lamps are operated in a well ventilated room the most im- 

 portant cause of variation is the humidity. Water vapor in the air 

 lowers the intensity of the flame and variations due to that cause may 

 exceed 15 per cent. Previous work at the Bureau of Standards^ has 

 indicated that 1 per cent, of water vapor in the air causes a decrease of 

 5.67 per cent, in the candle power of the flame, whereas the correction 

 officially established in England is 6.6 per cent. The present paper 

 gives further data based on about 75,000 individual photometer settings 

 on 27 lamps, including all lamps tested in 1911 and 1912 whose tests 

 have extended over a range of 0.5 per cent or more of water vapor in 

 the air. The mean result is an exact check of the correction factor pre- 

 viously found at the Bureau. 



To facilitate the reduction of observations to normal candle power a 

 ■chart is given from which the departure of a lamp from normal value 

 can be read directty when the barometric pressure and the readings of 

 the wet and dry bulb thermometers of a ventilated hygrometer are 

 known. The chart is plotted for a pentane lamp, but it may be applied 

 to other flames without introducing serious errors. E. C. C. 



GEODESY. — Triangulation on the coast of Texas, from Sabine Pass to 

 Corpus Christi Bay. Charles A, Mourhess. Special Publica- 

 tion No. 17, U. S. Coast and Geodetic Survey, 1913. 

 This publication contains the results of the triangulation of the U. S. 

 Coast and Geodetic Survey and the Engineer Corps, U. S. Army, along 

 a portion of the coast of Texas. The earliest observations involved in 

 this work were made in Galveston Ba}' in 1850, and the most recent work 

 was completed in 1912. The geographic positions of over 700 points, 

 all correlated to the same geodetic datum, are given, together with a 

 complete description of all permanently marked stations. A series of 



1 Rosa and Crittenden, Transactions Illuminating Engineering Society, 5, 

 753, 1910. 



