The Laws Observatory. 515 
IV. HEIGHT ABOVE SEA LEVEL. 
Three determinations of the height above sea level of this 
Observatory have been made by three independent methods. 
The elevation of the front door-sill of the Boone County 
Courthouse in Columbia was determined by Wabash Rail- 
road levels about the year 1868, and in 1892 the height of the 
bench mark at the Observatory was determined by reference 
to the courthouse door sill. The second determination was 
derived from four years of daily barometric observations 
made at the Experiment Station on the University Grounds 
and compared with similar observations made at St. Louis and 
Kansas City, Mo. In June, 1893, the elevation was again 
determined by running a line of levels from the Observatory 
to a bench mark of the Mo. Riv. Com. located on the north 
bank of the Missouri river at Providence, Mo. 
The Railroad Levels. The record of these levels has been 
burned but I have been able to secure the necessary data 
through the kindness of Professor G. C. Broadhead, formerly 
State Geologist of Missouri, and now Professor of Geology 
in this University. In a letter dated April 20th, 1874, 
written to Prof. Broadhead by Mr. Geo. C. Pratt, a civil 
engineer, then in the employ of the Wabash Railroad Co., it is 
stated that Mr. Pratt found from inspection of the records 
then on file in the offices of the company, that the elevation of 
the ‘‘ Columbia Courthouse’’ above the St. Louis City Directrix 
was 342 feet. Assuming the height of the Directrix to be 
405 feet, Mr. Pratt gives 747 feet as the elevation above sea 
level of the courthouse. The elevation of the St. Louis 
Directrix has been very accurately determined by the Miss. 
Riv. Com. and found to be 412.7 feet above mean tide 
level on the.Gulf of Mexico at Biloxi, Miss. This result 
has been confirmed by the U. S. Coast and Geodetic Survey, 
and gives as the height of the courthouse 755 feet. The 
Observatory Bench Mark is 24 feet lower than the door-sill 
of the courthouse, and therefore we get as the elevation 
above sea level of the Observatory Bench Mark 731 feet. 
