work, as well as surveys of rivers and streams, can be advantageously done with a transit having stadia wires or other means for obtaining distances. If it is desired to map both banks of a broad river, an excellent plan is to make the survey on the ice, setting the transit at stations 800 or 1,000 feet apart as near the center of the stream as may be determined by eye and using two or more stadia rodmen to take points along the banks; reading the limb from 0° to 360° and carrying the azimuth as in a traverse survey. This traverse should commence at and close upon previously established points in the base line system. The angles thus taken may be conveniently platted with a full circle protractor. These may be had about fourteen inches in diameter printed on drawing paper and graduated to quarter degrees, and are easily read to the nearest five minutes. The central part of this protractor should be cut away, so that a flap carrying the center point folds back out of the way after the protractor has been oriented on the drawing; allowing the readings to be plotted directly from a scale whose zero point is placed at the station point and whose edge is swung around to the given bearings.

There are three methods of engraving suitable for a large scale city map: lithography, the wax process and zinc etching. A lithographed map is put upon the stone in three general ways; by being redrawn on the stone reversed in lithographer's ink or "turch" from the original drawing, which must be in the same scale as the prints are to be; by phototransfer from a carefully lettered original drawing which must be totally void of color except dead black ink; or when the original drawing is executed in transfer ink upon transfer paper (to be had of any lithographer), a transfer may be made directly onto the stone.

Drawings for photo-lithography are preferably drawn to a larger scale than the finished prints are to be. The reduction to the desired scale is made by photography before transferring to the stone. This reduction serves two purposes, it sharpens the original drawing, or causes any slight roughness of the pen work to be less apparent, and it allows the letters and figures to be made on a larger scale, and hence with less difficulty by the draughtsman. The original drawing should not be more

than about one and one-half times what the finished prints are to be. Thus, if the scale of the printed maps is desired to be 400 feet per inch, the original drawing may be 300 feet per inch, or if 300 feet per inch is the scale desired, the original drawing may be 200 feet per inch. Much greater reduction than this is not advisable. Considerable skill in making the original drawing is required to obtain the best results by any photo-transfer process. The drawing must be clean and sharp, and the draughtsman must constantly bear in mind the effect of the reduction upon the width of the lines and the size and spacing of the letters and figures. The finest line should be perfectly black, though a slightly brownish tinge will not be injurious; but fine lines are the hardest to reproduce in the negative, and if they are lighter in tone than the heavy ones, presenting a grayish or brownish appearance, they are liable to be lost in the engraving.

The paper on which a drawing for photo-reproduction is made should be pure white in color, having a perfectly smooth surface, and must not be calendered or shiny; as the reflection from the surface would interfere with photographing. Bristol board is generally recommended for the purpose, but many samples of bristol boards pick up badly under a fine pointed pen, filling the pen with paper stock, and requiring constant cleaning. The writer has had better success with a heavy grade of unprepared blue print paper, the kind known as French satin paper. Hand-made drawing papers are inclined to cockle and contract unevenly after being damp stretched, which distorts the drawing. Then, too, the largest size of single sheet, 31x53 inches, is often too small.

The wax process makes a very neat map, as all letters and figures are in type. A smooth metal plate is covered with a thin coat of wax, the drawing is transferred to the wax, and the lines are engraved through the wax with pointed tools, to the surface of the metal plate. All letters and figures are made by pressing type through the wax until in contact with the metal plate. When the engraving is complete an electrotype is taken, which, as the drawing on the wax was a positive, will be a negative, and after blocking up is ready for the ordinary printing press. A wax process engraving of a city map

costs from ten to twenty-five cents per square inch. A city map on a scale of 400 feet to an inch, with dimensions of lots figured, and an average amount of railroad tracks, public buildings and water lining will cost from twenty to twenty-five cents per square inch to engrave by the wax process; which is the most expensive of the methods described for this kind of a map. For a small scale guide map of a city, showing no lot lines or numbers, the wax engraving is well adapted. Drawings for the wax process should be in the same scale as the engraving. Rand, McNally & Co., of Chicago, use the wax process almost exclusively.

For a zinc etching a finished drawing is made the same as for a photo-lithograph. This is photographed and a print made from a reversed negative on a polished zinc plate sensitised for the purpose. This zinc plate is then etched with acids so as to leave the lines in relief. A zinc etching costs from six to ten cents per square inch, and is best adapted to small maps, say up to twenty-four inches square. The reproduction of the original drawing by this process is very perfect, being usually somewhat better than by photo-lithography.

The inset sheets in Engineering News, each week, are reproduced by photo-lithography from enlarged drawings, and the outline drawings and diagrams occurring in the text are mostly zinc etchings. The style of letters and figures used on these drawings in Engineering News is especially well adapted to reproduction by photographic methods.

If it is desired to use flat tints in coloring the maps, the stencil method is the cheapest for a few hundred copies. For large editions it will be cheaper to print the colors in, necessitating a separate color stone or block for each color used.

Before making an estimate of cost of work which is to be redrawn on the stone, it will be necessary for the lithographer to see the copy, but for a photo-lithograph all he will need to know in order to furnish an estimate, is the size of finished maps, what coloring is to be done, number of copies wanted the kind of paper desired and style of mounting. Within certain limits the size of the map does not control the cost of a photo-lithograph job, as closely as it does with other methods of engraving. Hence, the photo-lithograph is to be recom

mended on account of its cheapness and the satisfaction of knowing that when the original drawing is completed and "checked up." that the prints will be absolute reproductions. Very few engraving houses who do no lithographing, do their own press work. It is quite evident that more satisfactory work can be expected when the engraving, printing, coloring and mounting are all done at one establishment.

Among the medium priced papers, book-paper is best adapted to lithographic map-printing. This paper tears rather easily, and requires a backing of muslin, i. e., it should be mounted. Line etchings print best on a highly calendered paper. Linen or bond papers are desirable on account of their toughness and durability, but are high in price and difficult to print upon.

Accurate property maps are a necessity to the business community, and the compilation of such a map can profitably occupy the time of a surveyor and his assistants when they would not be otherwise employed.

METHODS OF STONE QUARRYING.

H. G. ROTHWELL.

In treating this subject, I must confine myself more particularly to the sandstones, as my experience has been confined chiefly to these.

Sandstone on account of its wide distribution, its variety of colors, and its capabilities for cutting, carving, and finishing, both for plain and ornamental stone work in both public and private buildings, combined with its cost, in comparison to other classes of building stone, is one of the most largely used stones in the building trades.

The stone was deposited by nature in layers or beds, of varying thickness. In some instances these beds are so thick as to be called massive. The method of quarrying varies in its details somewhat to suit these conditions.

The principal form in which it is quarried out, is in what is

called dimension stone, say 8' +4'+2', or sizes approximating these figures, these blocks are sold by the cubic foot to builders and contractors, who cut them up to suit the various parts in the buildings erected. In getting out these blocks a considerable rubble stone is made, which is generally sold for a low figure or wasted.

Most of these sandstone quarries are covered over with a covering of glacial drift and shale rock varying in thickness from a few feet to fifty feet and even greater, these extreme depths, however, are not profitable as the cost of stripping the stone is too great, as all this covering has got to be removed before the stone is quarried.

The cost of this removal depends greatly on its nature and the facilities for wasting it.

After a stone quary has been stripped, the next process is to cut on the side on which it is proposed to open it, a channel, or more properly two channels, say about four feet apart and parallel, to the depth of the bed (if not too deep). This cutting is done generally by a steam channeling machine, of which there are many, such as the Wardwell, the Ingersoll Sergeant, the Sulivan steam channeler and Gadder, etc., all of which you will see illustrated in most all our leading engineering and mechanical papers. After these two channels are cut a portion is broken out or hand channeled across between the two channels, leaving a space from two to four feet wide according to the depth of the bed. This is called removing the key, and leaves a space in which the other stones can be moved as they are broken apart. This break is generally made by drilling two or three holes at right angles to the channels, and to nearly the depth of the bed, the stone can then be cracked or loosened by means of plugs and feathers (the old way), or by the use of the Knox blast. This process is the most modern and is a patented process, or rather the tool to do it with, which is a drill point that drills a hole larger at the bottom than at the top, making a chamber towards the base of the stone in which a small quantity of coarse blasting powder is placed, together with an electric exploder and the hole tamped, after which it is fired with a battery and the force of the concussion breaks the stone apart and moves it slightly on its bed. It then can be removed by the derrick.