Set the standard sludge box just below the floor of the shanty and in such position that there is room to siphon off the water and take out the sample without moving the box. Connect a tee to the top of the standpipe or casing and lead a pipe from it to the nearer end of the sludge box, at such a height that it will either be level or slant towards the sludge box and just rest upon the top of the box, and of such a length that it will not project more than one inch beyond the edge of the box. The pipe must not be more than two feet long, and if longer than one foot must be split on top for the foot nearest the sludge box, so that if sludge collects in the pipe it may be seen. Set the box level, so that water will overflow evenly across the whole width at the far end, and wedge the partition firmly, so that it is in close contact with the bottom of the box. The top of the partition should be one inch below the water level. The box is now ready to receive the sample, and drilling may be started.

While drilling, care must be taken that no water from the drill-hole escapes around or over the tee except through the pipe leading to the sludge box. Care must also be taken that there is no leak from the box and that the three-inch plug at the end of the box is tight. Sludge samples must be taken for every five feet drilled, or less, preferably from even five-foot intervals ; that is, from 460 to 465, 465 to 470, 470 to 475, etc.

Whenever a sludge sample is to be taken, drilling must be stopped and the hole washed out clean. The pipe leading to the sludge box must be cleaned out into the sludge box, and either the pump must then be stopped or the tee turned so that the water will not be discharged into the box. Carefully remove the partition in the box, so as not to stir up the sludge any more than necessary, and when the sludge is settled, siphon off the surplus water, being careful to keep the end of the siphon near the surface of the water, and not disturb or draw off any of the fine sludge at the bottom of the box. To use the siphon, fill with water a three-foot length of large size flexible hose, and with one hand on each end place one end beneath the surface of the water in the box and the other end on the ground eight inches or more below the top of the box. When both ends of the hose are released the water will flow out of the box, and may be allowed to flow until it is seen that the sludge is beginning to go off with the water. Then remove the hose and thoroughly mix the sludge in the box to a mud. This must all be removed from the box and placed in a pan on the boiler to dry. The pan must be at least 8 in. by 12 in. by 1 in. deep, with flat bottom, and must be thoroughly cleaned each time before a sample is put in it to dry. If enough water cannot be drawn oil without disturbing the sludge so that the sample can be contained in this pan, a larger pan must be used. All the sludge must be saved and the sludge box cleaned thoroughly. When the sludge has been cleaned out, remove the three-inch plug at the end of the box, and wash out the box with a pail or two of water, then replace the plug and partition, and drilling may be started again. The sludge must be labeled, giving the depths between which the sample was taken, when it is placed on the boiler to dry. It must all be saved and turned over to the inspector. Sludge must always be saved when drilling in iron formation or in any other ferruginous or red material. While drilling in material from which a sludge sample should be saved, if the water is lost, if the sludge does not come up with the water, or if the sludge is contaminated with material caving from higher up in the hole, drilling must be stopped immediately until the hole is put in such condition that good sludge samples can again be obtained, or until the inspector gives orders that drilling may proceed.

Whenever the drill runs into or out of ore, provided the band of ore or rock is one foot or more thick, drilling must be stopped, and the sludge box cleaned out immediately, without waiting to complete the five-foot run. When the drill runs out of ore continue taking and saving sludge samples for at least twenty feet, no matter what the material, so that it may be determined, whether the ore is caving.

Keep the core separate from the sludge, and each time core is pulled, label it with the depths between which it was recovered. Each run of core must be kept separate, and all core must be saved and turned over to the inspector. When the core is pulled, if it is found that more core is saved than the proportion of one foot of core to ten feet of drilling, the sludge box must be cleaned without waiting to complete the five-foot run, and the sludge labeled and saved separately. If sludge from a shorter distance than five feet is in the box at the end of the shift’s work, and if less than the above proportion of core is saved, the sludge may be left in the box, provided the shanty is locked and the box is inaccessible from outside the shanty. If anybody can get at the box, however, and if there is no watchman, the sludge must be removed from the box, dried, labeled, and placed with the other samples.

The standard sludge-box is shown in Fig. 10.

When the samples reach the office they are carefully examined, and a daily report of all drilling made out on the form shown in Fig. 11. Samples of all core and of all sludge which runs above 40 per cent, of iron are preserved in special cabinets in a fire-proof room. A few pieces of core are saved from each run, and the rest sent to the laboratory for analysis if the ore-formation has been cut, otherwise it is thrown away. A little of each sludge-sample is placed in a small pasteboard tray, with a temporary label, 10 ft. to a tray, until the analysis is completed. Each 10 ft. of sludge-sample which exceeds 40 per cent, of iron is then placed in a gelatine case 3 in. long by 1 in. in diameter, and preserved in the same drawer with the core. Gummed paper labels are used for both core and sludge.

Combination of Core- and Sludge-Analyses

When enough core is saved to make it worth while, and when the analyses of the core or sludge exceed 45 per cent, of iron, the results are combined according to a formula which gives proper weight to each, derived as follows:

Let A = diameter of bit outside of carbon, in inches.
B = diameter of bit inside of carbon, in inches.
C = feet of core saved in “ D ” feet drilled.
D = feet drilled.
S = volume of rock actually ground to sludge, in cubic inches,
T = volume of rock actually saved as core, in cubic inches.

To obtain an average of the sludge- and core-analyses, giving the proper weight to each, the sludge-analysis should evidently be multiplied by S, and the core-analysis by T, and the sum of the products divided by S + T. The result is the same and the operation simpler to multiply the sludge by S/T and the core by 1, and divide by S/T + 1; hence, the rule for an A bit is to multiply the sludge-analysis by 3.3 D/C – 1, add the core-analysis, and divide the sum by 3.3 D/C.

Only iron is run on the 5-ft. samples, with phosphorus if they contain more than 40 per cent, of iron, and manganese if exceeding 1 or 2 per cent. Occasionally, several of the 5-ft. samples are combined, and a complete analysis made for iron, phosphorus, silica, lime, magnesia, alumina, manganese, sulphur, titanium, and loss by ignition.

After combining the core- and sludge-analyses, the results are further averaged in continuous runs of ore of the same grade. We call from 45 to 50 percent, of iron “lean ore,” 50 to 57 per cent’. “ second-class ore,” and more than 57 per cent. “ first-class ore.”

Representation of Results

As soon as possible after the first of the month, the record of material drilled during the previous month is compiled from daily reports and averaged analyses. This result is carefully checked with the core and then recorded permanently in the drill-book, which has loose leaves, with pages of the form shown in Figs. 12 and 13. The reports of the drillmen and analyses of samples are copied in this book daily, and it forms the complete and permanent record of drilling. From this book tracings are plotted from which blue-prints are made. Figs. 14 and 15 show the printed forms on tracing-cloth used for this purpose. The tracings are 14 by 16 in. in size, the same as that of the loose-leaf sheets in the drill-book, and are bound in covers of the same size.

Cross-Sections of Drilling

For the scientific location of drill-holes, cross-sections must be made through outcrops and previous drill-holes, preferably at right angles to the strike of the formation, showing the holes plotted according to the surveys for inclination and course, and showing the material encountered. We make these on cross-section tracing-cloth ruled in inches and tenths, on a scale of 50 ft. to 1 in. The sections may be superposed and compared, and the cross-section ruling makes it easy to read distances and areas without a scale. On these tracings the geological boundaries of formations and the outlines of ore-bodies are drawn in soft pencil, which prints satisfactorily, but may easily be erased and changed if further drilling shows the first assumptions to be wrong. When necessary, longitudinal sections are made, which, in connection with a plan and cross-sections, give a very good idea of the structure of the deposit.