344 



CEMENTS, LIMES, AND PLASTERS. 



When the marl occurs in an old lake-bed overlain by soil or peat, the 

 area can be roughly laid out into blocks or squares of convenient size, 

 borings being made and samples taken at the corners of these squares. A 

 pocket compass, or, better yet, the cheap "drainage level" made by 

 Gurley and other instrument-makers, will suffice for laying out the work. 



A marl deposit covered by water must be handled like any sound- 

 ing proposition. The shore line should first be roughly surveyed, after 

 which soundings and borings must be made from a raft or boat, the 

 position of each boring being located by bearings taken to fixed points 

 in the shore. A broad steady platform is necessary for the borings. 

 This is afforded either by using a raft with a square opening in its center 

 or by laying planks across the ends of two boats. 



As the methods employed in determining the thickness and char- 

 acter of marl-beds are of a somewhat special character and are not 

 fully described in current engineering text-books, the writer feels justified 

 in introducing here a very detailed account of these methods by Mr. 

 David J. Hale, of the Michigan Geological Survey. This account is 

 taken almost verbatim from the paper cited below.* 



In dealing with fairly solid marls not deeply covered with peat 

 or soil, the simple outfit described below has proven very successful 

 when manipulated with care. It is prepared as follows: 



Weld an ordinary 2-inch auger on a f-inch gas-pipe 2 feet long. 

 Thread the unwelded end of the pipe for coupling. Cut three lengths 

 of pipe each in half or in four pieces if it is desired to carry the outfit 

 long distances. Thread the ends of these sections for coupling. Get 

 couplings enough to couple all together, so as to make a continuous 

 hollow rod with attached auger. Insert a "T" coupling on the handle 

 end, or end farthest from the auger, and pass a rod or stick through 

 this so as to turn the outfit. A better way is to screw into each free 

 end of the "T" a rod or piece of gas-pipe 18 inches long. Usually a 

 pair of Stillson wrenches are needed to untwist the pipe, which becomes 

 jammed during the boring. 



Three-eighths-inch pipe, as above recommended, will be found to lift 

 out much easier than half-inch, but will not do for deep borings-inch pipe 

 is entirely too light and 1-inch pipe is too difficult to handle. A light, 

 easily handled outfit is a great aid in boring, because the quicker the rod 

 can be driven the less friction there will be to contend with, for the marl 

 particles will not have time to settle after each movement of the rod. 



* Hale, D. J. The use of marl for cement manufacture. Vol. 8, pt. 3, Reports 

 Mich. Geol. Survey, sspecially pp. 9-13, 108-110. 



