when the changes of structure induced in the metals affected are fully known. In such cases the application of the microscope renders a most valuable aid in elucidating the source and nature of these changes, inasmuch as it reveals to the eye

AN IRON CRYSTAL. Seen under the Microscope.

the altered configurations of the constituent bodies.

The most important results of the microscopic investigation of metals have been obtained from the study of alloys, whose properties largely depend upon their physical constitution. The alloy at present claiming chief attention is steel, with its great variety of structures, differing not only with each content of carbon, but also with that of other constituents either adventitious or purposely added to produce a given effect. That the nature and arrangement of structure is by far the most important factor in determining physical properties, is becoming more evident every day; and most of the researches of metallographists are conducted on this assumption, for it certainly enables one to explain many problems otherwise insolvable, such as the cause of cracks, breakage, and other defects in samples of similar chemical composition.

Another illustration may be taken from the case of the bearing metals used for reducing friction. These alloys are found to consist of different constituents varying in hardness; and the load of the journal is carried through them by the hard component of the alloy, which is found

to possess a low coefficient of friction, the plasticity of the matrix making it possible for the bearing to adjust itself closely around the shaft. The plasticity may be ascertained by means of compression test, but the nature of the constituents must be determined by microscopic examination.

The manner in which crystalline structure in metals is developed varies; but the main factor is temperature. The more slowly a metal is cooled from the melting point, the larger will be the dimensions of crystals, the more perfectly will they be formed, and the more symmetrically will they group themselves together. On the other hand, if a metal be submitted to pressure, not only will the individual crystals be distorted, but the orderly arrangement of the whole mass will be disturbed; and when the pressure is carried to a certain extent, the metal will become so weak as to be easily fractured by a slight additional force. Now, as the crystalline condition is the natural state of a metal, any deviation from this will be unnatural. In that case the molecules are ever tending to pass back again to the normal state, which is perfectly effected by remelting.

When a piece of iron is strained in tension, its crystal grains become elongated in the direction of tension; but when the specimen has subsequently been annealed

face of the crystals, parallel to one another in each crystal, but in different directions in different crystals. They then look like a crevassed glacier, and the lines like cracks. These lines, however, are not cracks, but "slips" along the cleavage, or gliding planes, and are termed "clip-bands." Such bands are produced also by compression or torsion, and it is in virtue of this action that plasticity in metals is possible. Prolonged annealing tends to produce large crystals in iron and steel, but even a short exposure to

a suitable temperature produces complete recrystallization.

For the exact examination of the structure of metals with the microscope, it is necessary to have the specimen perfectly flat and free from scratches, as scratches tend to mask the real structure; further, flatness enables all the parts to be properly focused under the microscope-an indispensable condition when photography is used. The section, for convenience, should be about half an inch square and one-eighth of an inch thick.

age maximum wages received by them. Further, President Dodge finds that the unskilled man has reached his maximum earning capacity of $510 at the age of 22 years. This, capitalized at 5 per cent, gives him a potential value of about $10,000. The shop-trained man reaches his maximum of $790 per year at 24 years of age. The wages of the technical school graduate are still rising at 32 years of age, when he receives an annual income of $2,150, which gives him a potential value of $43.000 when capitalized at 5 per cent.

The accompanying diagram, prepared from data received from graduates in Electrical Engineering of the Worcester (Mass.) Polytechnic Institute, substantiates the conclusions of President Dodge, and further emphasizes the ad

very completely the financial prospects of technical graduates from year to year. The Department of Electrical Engineering of the Worcester Polytechnic Institute has been established but eight years, and hence there are data available for this period only; but during this time a large number of students have graduated, and data have been received from a sufficient number of them to make a fair representation of existing conditions. From the curves it is seen that the average graduate who receives $500 per year for his first position after leaving the Institute, rapidly increases in value, so that at the end of eight years he may expect to receive an income of about $1,900; or if he has been a graduate student for one year, his income is shown to average about $2,500, which, capitalized at 5 per cent, gives him the income on an investment of about $50.000. By investing five years of his time and the cost of his college training, he has, after a few years, and for the remainder of his life, increased his income-earning value by not less than $40,000. That the investment is a good one, goes without saying.

T

HE SUEZ CANAL has been in existence for so many years that in a large measure the public fail to realize that its commercial importance is still in its infancy.

The thin ribbon of water which unites the Orient and the Occident, we recognize as a great engineering feat of the past; but the fact that vast schemes to develop this international property are going on under the direction of the Suez Canal Company, is something that seems to be lost sight of in the newer interests of the Panama Canal.

It is at Port Said, at the Mediterranean mouth of the Suez Canal, that this development is most apparent. The old, ill-famed, dirty town, full of the human scourings of the Levant, has given place

a comfortable city of well-wooded streets and many fine buildings. Along the water-front there still stretches a medley of one-storied houses, but the directors of the Suez Canal Company are laying plans that will in time transform Port Said into a Mediterranean Singapore.

On both sides of the northern end of the canal, and on what is generally, although inaccurately, known as the African side, the existing dockage in the Arsenal and Commercial basins is to be greatly enlarged. On the eastern bank a very much larger project is in contemplation. The directors have decided on the immediate construction of an enormous coal dock, 2,112 feet in length and 1.137 feet in width. This will take the place of the existing basin.

Another matter affecting Port Said is the continual choking up of the entrance to the breakwater, owing to the strong easterly current along the shore of the delta at the mouth of the Nile. This water, of course, is heavily charged with alluvial earth, and the deposit sometimes. exceeds one and a-half inches in twentyfour hours. To overcome this, two of

the most powerful dredges yet designed have been constructed, and have proved themselves capable of dealing adequately with the deepest deposits.

Another important improvement is to be the relaying of the narrow-gauge railroad which runs from Port Said to Ismailia. This road was originally built as a construction line for the use of the workmen on the canal; but, as the trade of Port Said has increased, the traffic has become so great that the directors have decided to lay a 4-foot 8-inch gauge road, and to run their trains in connection with the Egyptian government rail

way.

Within the next five or six years, the Company hopes that the canal will be widened to its utmost limit so that the largest ships will then be able to pass each other at almost any point between Port Said and Suez.

Dredging has already deepened the canal to the uniform depth of about 28 feet, and it is the purpose of the directors ultimately to have a clear foot of water below the bottom of the largest steamer that has yet been launched.

It has also been discovered that the fringe of reeds which grow on the African side of the canal below Ismailia, forms a better protection for the banks than the courses of expensive sun-dried brick or sandstone in use elsewhere. An attempt has been made to grow these reeds in other parts of the canal; but the difficulty has been found that the reeds, although they will afterwards adapt themselves to and flourish in salt water, must originally be grown in fresh water, and there is no fresh water on the Asian shore of the canal from end to end.

Another achievement of the Canal Company is the stamping out of malaria. at Ismailia, and turning one of the most fever-stricken spots in Northern Africa into a health resort. This was accomplished by Dr. Ross, by filming over with