The roundness of pebbles has been measured for the purpose of finding the effects by abrasion and transportation in streams. In the lower course of ten rivers : the Abe, Oi, Kiso, Nagara, Ibi, Sho, Tedori Rivers in the Chubu District, and the Inugami, Hino Rivers in the Kinki District and Monobe River in the Shikoku District, two or three stations were chosen for sampling the pebble population, where we have measured the size of sediment and roundness of pebbles 32-64mm each of some kinds of rock types. The results obtained for these values are given in figures 3 to 13 shown by mean size, mean roundness, and ratio of roundness in each rock type with distance of transport. From these figures we considered the cause of abrasive action accompanying transportation. Their results are as follows:
(1) On the relationship between roundness of pebbles and distance of transport in the same rivers, it is clear that the roundness differs with rock types. For example, it is clearly shown that the roundness of limestone is to increase rapidly downstream, but that of chert little changes is the roundness. The analysis of roundness diagram which shows the relation between ratio of roundness and distance of transport explains the abrading processes. Hard rock, such as chert, quartz-porphyry, liparite or graywacke, is worn mainly by chipping and grinding. On the other hand, soft rock such as granite, slate and shale, brings about the exfoliation, and is worn more by splitting and crushing than hard rock.
(2) This study of the roundness of pebbles, by means of using graywacke which is found in many rivers, shows that the steeper the gradient of the river floor is, the more the roundness of pebbles is. The cause seems to be a rapid flow, variation from streaming to shooting in a stream form or increase in the intensity of turbulence on the steeper gradient of a river. But, on the Oi River the mean roundness shows no change downstream in spite of the steep gradient of the river floor. This may be that turbulence weakens the attrition of pebbles, as the river is wide downstream.
(3) The ratio of the loss in the weight of pebbles varies with the river property, distance of trans-portation, and rock type. In the estimation by roundness, it seems that the loss in the weight of pebbles is about 7 per cent as far as the mouth of a canyon and 9 per cent as far as the mouth of a river in Japan. Moreover, on the basis of the results obtained from the estimation, selective transport accounts for 93 per cent of the size decrease and 2 per cent is accounted for by abrasion in the lower course of the river in Japan.
(4) The ratio of gravel to sand in sediment has not so much effect on the attrition of pebbles as gradient of the river floor. For one thing, it seems that the ratio of sand in sediment in the river in which the roundness is measured, is about 10 per cent in difference. But, the former studies are made in the river where there is found no sand or much sand. Therefore, the relation stated above is only found in an extremly different ratio of sand.
(5) The order of resistance for abrasion obtained from roundness is as follows: chert is heighly resistant, liparite, and quartz-porphyry are resistant, graywacke is moderate, granite, shale and slate are less resistant, and limestome is small. This order coincides to that of Kuenen's one.

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(1) The fact, that the water temperature in the deep layer of lake is governed by its surface area or fetch size, had been discovered by the late Dr. S. Yoshimura. But he did not relate the heat budget of lakes to their scales. In this report, several relations between the thermal peoperty of lakes and their scales are discussed.
(2) The depth of thermocline (D) or surface layer (De) (epilimnion) of lake differs greatly accord-ing to the scale of lake in summer. Actual values of D and De are decided from the vertical temperature profiles following Lund's method. The relations between D or De values and the fetch size of lakes, are presented in Fig. 1, which shows 1/3 power laws. Concerning several Japanese lakes, the empirical relationship D=6L_??_ is obtained from the author's data and Horiuchi's results in the summer season. In the two adjacent lake basins of Shinsei-ko Pond near Tokyo, vertical temperature profiles were measured to compare the effect of fetch size on the profiles. The results of observations are shown in Fig. 3.
(3) Annual heat budget of lake (∑Q) ie calculated by the following formula.
∑Q=C•_??_dt•dz
Because water temperature in the surface layer of lake in summer (θ_max) does not differ greatly by the seale of lake, and the same tendency is recognized in mid-winter (θ_min), so the numerical value of ∑Q is approximately represented by functional form of D.
∑Q_??_(θ_max-θ_min)D=const₁•D_??_L_??_
The relation between ∑Q values and the fetch size of lakes is shown in Pig. 4, which supports the pre-ceding considerations at least concerning Japanese lakes.
The surface water temperature is decided by terminal temperature in a shallow pond, but in a large and deep lake discrepancy between the surface temperature and the terminal temperature (θ_∞) becomes evident. This tendency is more remarkable in a large lake than in a small one.
On the other hand, heat balance consideration being introduccd to the above discussion, heat balance equation i s given by the following form;
∑Q=R_n-H-LE
where R_n represents net-radiation, H and LE show sensible and latent heat exchanges a t water surface. As there are no remarkable differences of solar and net-radiation values all over Japan from spring to autumn seasons, we can assume the following relation as an approximation.
(∑Q-R_n)_??_-const₂•D_??_L_??_ This tendency is also examined by the other calculations, using heat transfer coefficient and air-water temperature differences (Fig. 7). Numerical value of the transfer coefficient is 2×10^-4ly/sec. °C in this case.
From these considerations, it is found out that the evaporation from lake surface (F) in the spring and summer seasons in warm and cold regions decreases in proportion to the scale of lake.
(4) The thermocl.ine of lake does not appear in tropical region where annual variations of terminal temperature and heat flux are very small. In this region, the lake temperature remains almost isothermal throughout the year. Above discussions state that the terminal temperature is not the true surface tern. perature, but in this case we may take θ_∞ value as the first approximation of surface temperature. In Pig. 8 annual variation of θ_∞ values at several stations of the world are shown with the world distribu Lion of the value (Fig. 9).

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In order to investigate the cause of local variation in sea cliff retreat, the author surveyed the sea cliffs along the Pacific coast of Ohmika, Haranomachi City in Fukushima Prefecture, Japan (Fig. 1). Throughout this coast of 3 kilometers in length, we find sea cliffs with a height of 5 to 25 meters. Most of them are 20 meters high cutting a marine terrace, but some of them at the northern part are found on a side of another lower fluvial terrace, which is about 5 meters high. An obtuse angled cape divides this coast into two: northern and southern parts (Fig. 2).
Judging from the old (1912) and the recent (1959) maps of this area, it is possible to recognize a clear difference of the land area lost between the northern and southern parts (Fig. 4). The southern part showed more loss than the northern one, though the former has a wider beach in general. Moreover, there is a difference in type between the northern and southern cliff profiles (Fig. 3). The northern cliffs are almost everywhere characterized by a vertical bluff just like a wall showing a smooth face. Deep sea-caves at their foot and narrow stepped platforms in the middle of the cliff profiles also can be seen at some places in thenorthern part. On the other hand, the southern cliffs are rough and vertical at the lower part and also quite steep, but not vertical, at the upper. There are no sea-caves but shallow notches at their foot. Wave-cut benches could be seen at the foot of the cliffs in the southern part.
As regards to the fallen debris at the foot of these cliffs in the southern part, a large amount of all sizes having fresh faces and sharp edges are to be found. On the contrary, in northern part, there are less debris but most of them are larger and well-rounded.
As for the geology of this coast, they consist generally of sand and gravel deposits at the upper, a sandy mudstone layer at middle and lower (Fg.5). At the southern part, this sandy mudstone layer is divided into two by an inserted unconsolidated stratum of sand, and this sandy stratum locates just at the foot of the southern cliffs, The middle and lower parts of the northern cliffs consist of only homogeneous mudstones.
To know one of the resisting powers of these strata against wave attack, the author measured hardness for every stratum on the southern and northern cliffs by using a penetrometer, an instrument for measuring soil consistency (Tab.2). The strikes and intervals of the joints in the mudstone layers are also important factors for destruction of the cliffs by storm waves. In the southern part, the strikes are oblique to the present shoreline. On the contrary, the strikes of the northern cliffs are parallel to the shoreline.
Other factors concerned with destruction of these cliffs such as wave, wind (Fig.7) and shallow water topography (Fig.6) were also examined, but the author considered that they are not so much concerned with the difference of cliff retreat as geological factors in this coast are.
Finally it was proven that the main cause of local variation in cliff retreat, and cliff profiles between the northern and southern parts on this coast depend mainly upon the geological factors, such as differences in stratigraphy, joints in mudstone layers and hardness of strata on this coast.

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