perpendicular to GH. From the point F five millimeter spaces are marked off on GH in each direction. Two other lines XY and MN are drawn parallel with GH at distances of 10 and 5 mm. respectively. The alternate points on the GH line are then numbered according to their distance in millimeters from the zero point F (10, 20, 30, etc.). From these points lines are produced toward E, to meet the line XY. The intermediate points. are connected in the same way with MN. Since all measurements are to be made at a distance of 100 ft. from the object, and the line EF is 100 mm. long, each millimeter space on the base line corresponds to I foot in the vertical height of the object The scale, as drawn, is therefore capable of measuring elevations 175 ft. above the level of the observer's eye and 50 ft. below. If the figures on the scale are printed reversed (as seen in a mirror) they are more easily read. In order to read the scale while the eye is sighting the extreme of the object along the line AC, a mirror consisting of an extraheavy tin plate is attached to the wooden block near the end CD. The tin plate is 24X10.2 cm. and the orfe end is bent around a wire 2 mm. in diameter and about 15 mm. long. At this stage in the construction the wire should extend beyond the edge of the tin plate only on one side. Two screw eyes having an eye diameter of about 2 mm. are then inserted in the wooden block, 1 cm. from CD and 10.3 cm. apart. The wire of the tin plate is FIG. 2. forced into the two screw eyes and the wire cut off flush with the screw eyes. This allows the mirror to rotate about an axis parallel with the line EF. A red silk string 22 cm. long, having at one end a rather heavy lead bob, is attached at the point E. Red is used as it contrasts well with the black lines of the scale. Figure 2 shows the complete instrument. MEASURING THE HEIGHT OF TREES. In using the hypsometer to measure the height of trees it is essential to have either a 100 ft. tape or better a 100 ft. piece of paraffine sash cord. Two persons are required, one to carry the end of the line to the tree, the other to hold the opposite end of the line and make the measurements. Since the instrument is held several feet above the ground at the eye of the observer, and because the ground is rarely level, it is necessary to make two readings, first pointing the hypsometer (line AC) to the top of the tree, and then to its base. In Figure 3 the eye of the observer is at E and on sighting the point A, the plumb line indicates on the scale the height of the point A above the level of the eye (EC). On sighting B the instrument is tilted forward so that the plumb line hangs on the opposite side of the perpendicular, and indicates the distance of the point B below EC. Obviously, the height of the tree is sum of the two numbers. If the observer stands below the level of B, both numbers are indicated on the same side of the perpendicular and the height of the tree equals the difference between the two measurements. FIG. 3. Where data in addition to height are desired it is convenient to have the person at the tree end of the line measure the diameter, identify the species and keep all the records. TOPOGRAPHIC SURVEYING. In topographic map making, it is necessary to divide the tract into hundred foot squares, with a staff compass and tape. Stakes are driven at each corner of a square. Some convenient point, preferably one whose elevation above sea level is known, is then taken as the base point and all height measurements are made with reference to it. Two persons are again required, one to read the hypsometer, the other to carry a staff having a target (such as a handkerchief) fastened at the same height above the ground as the observer's eye. When the staff is held at station B, the observer at station A records the relative height of the target as indicated by the hypsometer, using + and — signs to denote height above or below his own level. Assuming that station C is on the same line with A and B, its elevation will be measured from B and recorded in the same way. As soon as the relative measurement is made, the absolute height should. be calculated and marked at the proper corner on the outline map carried by the observer. For example, station A is 870 ft. above sea level. Station B has a relative height of +8. This should be recorded on the map as 878 ft. Station C has a relative height from station B of -10 This should be recorded as 868 ft. By changing the scale, the instruments may be readily adapted to the metric system and to the measurement of larger or smaller objects, at greater or less distances. The addition of sights to the side AC increases the accuracy of the readings. The coke production of the United States in 1905, which included the output from 3,159 retort or by-product ovens, amounted to 32,231,129 short tons, as compared with 23,661,106 short tons in 1904. The increase in quantity in 1905 from 1904 was 8,570,023 short tons, or 36.22 per cent. The total value was $72,476,196, as against $46,144,941 in 1904, a gain of $26,331,255, or 57 per cent. The average price per ton in 1905 was $2.25 against $1.95 in 1904. The average output from the by-product ovens in 1905 was 1,158.8 tons per oven, against an average of 365.8 tons per oven from the beehive ovens. NEW APPARATUS. BY THOMAS B. FREAS. Kent Chemical Laboratory, the University of Chicago. c a DISSOLVING TUBE. The This apparatus (Fig. 1) is designed. for dissolving solids which are difficultly soluble without the aid of heat or mechanical agitation, and filtering the solution at the same time. tube as shown in drawing consists of a cylindrical tube (a) for containing the solid. From the bottom of this a tube is attached which is of proper length to reach to bottom of bottles. in which the stock solutions are contained. From the side near the top a side tube (c) is joined which connects with the tube (d), which is a short extension of (a) and forms a jacket for (b). The apparatus has at (e) a cavity for holding a plug of cotton or asbestos wool for filtering. The dissolving tube is held by a rubber stopper which has an air vent cut on the side. The bottle is filled with water and the proper amount of crystals, are placed in (a), a plug of cotton or asbestos wool having previously been packed in (e). A suction by pump or the mouth is applied at a stopcock (f) in a light rubber stopper and the liquid from the bottle is drawn to fill (a) over the crystals. The stopcock (f) is now closed. The solution immediately travels down tube (b) because of its greater specific gravity and the water being lighter travels upwards through side tube (c). This will continue until all the crystals are dissolved or until the solution becomes saturated. The cotton or asbestos b FIG. 1. plug serves to catch any sediment which may occur with the crystals. Those laboratories which keep up stock solutions for general use find that there is no little labor in preparing these. Copper sulphate and potassium bichromate, etc., must be heated in an evaporating dish or agitated by shaking frequently in order to cause solution. By means of a tube of the above description a bottle of a solution of the strength ordinarily used may be prepared with little labor by allowing to stand a few hours. DROPPING GENERATOR. The drawing (Fig. 2) will show readily how the apparatus is constructed. It may be used for dropping some liquid upon a solid or liquid contained in the Erlenmeyer flask, in order to generate some particular gas. With the ordinary dropping funnel difficulty is nearly always met in obtaining pressure enough to force the gas through the wash bottles and further train used in the operation. With this apparatus the pressure of the flask below is transmitted to the dropping funnel above. The stopcock at side is intended to prevent escape of gas if refilling the dropping funnel bulb should become necessary. This cock may be omitted very satisfactorily. Where a solid is used in lower Erlenmeyer flask it is desirable to have it in the form of paste if possible, especially if it be necessary to heat the Erlenmeyer flask. The heating should be done with a very small flame. The apparatus is very quickly set up and one will be found convenient for generating many gases. The following may be prepared with this generator very readily: COHCl (dil.)+NaHCO FIG. 2. O-H2O+[Oxone (fused Na:O:)] |