From the time of the reopening of the country in 1854, Japan made great efforts tocatch up scientifically and technologically with the western countries, and in a relatively short time she seemed to have succeeded. For this, the tradition of Dutch learning in the nation paved the way and the foreign teachers who served in Japan played an important part. Americans were foremost among them. In the field of natural science at a collegiate or semi-collegiate level, nearly one third of them were Americans. The institutions where they taught were the newlystarted University of Tokyo or its predecessor and the Sapporo Agricultural College. Those American science teachers who were in office there for some time during the culminating years of 1871-90 numbered 14 at Tokyo and 6 at Sapporo.(Teachers who taught applied sciences soley are not included among them.)
As to these American science teachers, except for some, rather little was known until the present author succeeded in discovering their writings and biographical accounts in America. On the basis of these materials, it may now be said that they were well qualified teachers and many of them later became prominent as researchers, educators, or other professionals.

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In this paper the compressive deformation of an elastic solid in which contains a penny-shaped crack is considered in order to explain the brittle fracture of rocks. The complete stress-strain curve derived here consists of a linear proportional part with effective Young's modulus and fracture locus or so-called Griffith locus. The cross point of the former and the later gives a starting point of crack dislocation which is determined from Griffith's criterion.
Griffith locus expressed in equations (24) or (28) corresponding respectively to uniaxial and triaxial compression shows following features.
(1) It is a continuous curve whose slope is positive in a part and is negative in other.
(2) It varies with confining pressure, while depends on intrinsic physical constants of solid and geometric parameters of crack.
(3) If the initial crack size is smaller than a critical value, given in equation (29) in uniaxial compression, the elastic body may sustrain unstable fracture.

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This paper propounds a new suction dredge. The points knowing this suction dredge from regular suction dredges are in a special suction-head attached to the forward end of a suction pipe joined to a sand pump, in a venturi-type detector of concentration in the suction pipe, and in the mechanism of automatic control for concentration.
The structure of the special suction-head may be mentioned as follows. A body finding a shape in which circumferences of two circular cones (or convex surfaces) stick together mutually is fixed in the inside of a conical suction pipe, with keepingth e suitable space between the body and the conical suction pipe, and a mouth is at the center of the convex bottom surface of the body.
In the suction-head, the convex bottom comes in contact with sand bed. When pressurized water is poured through the mouth into the sand bed, the sand bed of some thickness under the suction-head causes phenomenon of quick sand, and the suction-head may suck up sand of quick sand state. As a result, the suction-head goes down due to its own weight, and may suck up sand falling down about circumference of the suctionhead.
When flow of the pressurized water stops in the suction, the suction-head also stops going down into the sand bed, and sucking up sand.
The automatic control for concentration in pipe in pumping up sand-water mixture from the sand bed is done by on-off operation of the flow of the pressurized water, and upward and downward movements of the suction-head in a vertical line, which are controlled by signal of concentration in pipe being out-put of concentration meter.
This paper discusses theory of operation, static characteristics, and dynamic characteristics of the dredging of loose and thick sand bed by means of the suction dredge.
The tests of the laboratory model of the suction dredge built as a trial showed that automatic control for concentration in pipe is done successfully.

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An On-stream size measuring equipment has been developed for flotation pulp. It uses both vibrational output and light absorption. Sample flows into the vibration detection cell and next into the light absorption cell.
The vibration pickup detects very weak signals that are produced by collisions of particles and the cell. Effective signals are separated through an acoustic filter from noises.
The cross section area of light absorption cell is 1.3 cm² and light pass length is 3 mm. Suitable pulp density for this cell is about 4 wt%.
Several kinds of closed circuit tests have been done using SiO₂ and complex sulphide ore particles. From these tests the following results were obtained.
1) When n value of Rosin-Rammler distribution function of samples remained nearly constant, it is possible for this equipment to measure the size distributed samples as well as size sorted samples
2) When the variation of pulp density is limited in narrow range, an on-stream size measurement is attainable by the vibrational output only.
At the pilot plant tests, -200 mesh% of flotation pulp were measured by this equipment. The results of on-stream measured size, compared with screen analysis, were as follows.
Number of samples 109
-200mesh%(mean value) 73.91%
Mean square root error 2.03%
Correlation coefficient 0.923

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In this paper, we, the present authors, will describe the experimental and theoritical studies of the crushing mechanism of a single toggle jaw crusher.
In this research, the following results were obtained;
(1) In crushing with the crusher, the crushing load is influenced by the component of velocity of the movable jaw face that gives the compressive load.
(2) If the diameter of each spherical test piece is constant, the component of velocity is decided by the angle of a nip and the number of revolutions per unit time made by the crusher.On the other hand, about the theoritical studies, we will describe the internal stress of the lump of rock loaded by jaw crusher.
And this research were made as to the following problems;
(1) The stress from the elastic learning point of view on the supposition that the sphere is a disk of two dimensions.
(2) The direction and the position of the breaking line.
(3) The stress on the center of the breaking line.
In order to confirm these analyses, the method of photoelasticity was adopted in the experiment

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In this experiment, the current density of the oxidation and the reduction, the amount of electricity of the lead dissolution from the anode, and the diffusion coefficient of H₃O⁺at a fast step reaction were measured, using a platinum electrode and the potential scanning method, to determine the influence of the dissolved oxygen and the surface active agent in the lead electrolyte.
The results obtained are as follows:
1) It was shown by anodic scanning that the dissolved oxygen in the electrolyte has an effect on the form process of the oxygen adsorption layer and the evolution process of the oxygen.
2) The amounts of electricity of lead diffusion from the anode are constant in the concentration range of 60-100 g/lH₂SiF₆, but the amount of electricity increases proportionally with, the lead concentration. The effects of the surface active agent on the amounts of electricity were studied.
3) It was observed that the diffusion process of H₃O⁺, indicated by a peak I h, exists in the cathodic scanning wave, except in case of added phenol in the electrolyte. The diffusion coefficientD_Hof H₃O⁺is influenced by the concentration of Pb, H₂SiF₆and surface active agent, and in this experiment, the value of the region of 0.92×10^-6cm²/sec-0.50×10^-5cm²/sec was obtained.
4) The relation of the current density and the potential of the peak by multiple regression analysis were analysed. The resulting ratios of Iph equations obtained were about 80 percent in case of the added protein in the electrolyte.

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