Predominance of mandarin orchards and tea gardens is a typical landscape on the Pacific coast of Shizuoka Prefecture. They are distributed not only on the climatically advantageous coastal strips but also some distance inland along river valleys where climatic conditions are less favourable. Mandarin having economical advantages over tea in recent years, there has been a tendency that mandarin orchards replace tea gardens, or even paddy fields in this region. A distinct contrast in the distribution patterns of mandarin orchards and tea gardens can be observed along the River Okitsu within a relatively short distance. The valley, only 20 kilometers in length, can be divided by the presence of a narrow gorge in the halfway into the upper and the lower parts (Fig. 1). The lower part is characterized by predominance of mandarin orchards. They cover the greater parts of the sunny side of the mountain slopes and the valley floors as well, although the floor has only recently been turned into mandarin from paddy fields. Tea gardens are found only on the windswept ridges. On the contrary, the upper part of the valley is quite dissimilar in that mandarin orchards are concentrated to the height of 200400 meters above sea level and tea gardens are distributed both on the ridges and on the lower parts of the slopes (Fig. 2 and Photo 1). There seems to be no such tendency for the tea gardens in the valley bottom to be replaced by mandarin. This areal difference in landscape is expected to be accounted for, at least partly, by the different local climatic conditions. Two of the students of Tokyo Metropolitan University, S. TAKABAYASHI and H. KITAJIMA, conducted some meteorological observations along the valley and reported the results in manuscript forms. The authors try to supplement their works and to make a further discussion in this paper. The observations were made mostly during the nighttime in different seasons. Bimetal thermographs and mercury minimum thermometers were installed at different heights (ranging from 90 meters at the valley bottom to 400 meters at the top) of the slopes, and simultaneous temperature observations were carried out at some 20 localities with the help of high school pupils and university students. In addition, moving observations was conducted by using a thermister thermometer installed on a car. Temperature inversion was commonly observed on clear nights in the colder seasons both in the upper and the lower parts of the valley, whereas it seems to be absent in summer. Particularly in winter the temperature difference between the valley bottom and the upper part of the slope (relative height being 250 meters) may reach 4.0°C or even greater (Fig. 3 and 4). The top of the inversion was not ascertained by the observations, but the ridge appear to be cooler irrespective of the altitudes. There was no significant difference in the intensity of the inversion between the upper and the lower parts of the valley. Presence of temperature inversions itself does not explain the difference of the mandarin distribution. The explanation seems to lie in the fact that there is a remarkable difference in temperature. Many of the simultaneous observations revealed that there is a greater temperature gradient near the boundary between the upper and the lower parts of the valley (Fig. 5). In other words, the valley bottom of the lower part is much less frequently exposed to low temperatures. On the contrary, the upper valley is filled up with cold air, which is not easily drained out to the downstream. Consequently a typical cold air lake results, and the valley bottom there is subject to extremely low temperature.
A hand-written copy of one of Tadataka Ino's map of Japan was first introduced to European people by Dr. Ph. F. v. Sieboldt. Original Iro's maps showed only the differential longitude counted from the local prime meridian passing through the former site of the Institution of Calendar Reform at Nishi-Sanjo-Dai in Kyoto, but the very copy of Dr. Sieboldt was budged with the value 135°40′ as the value of the east longitude of the said prime meridian counted from Greenwich. In this paper, I have tried to explain how such value was obtained by Japanese astronomers. After examining values of then existing or known values of the longitude of Japan, I arrived at the conclusion that the value 135°40′ was not those derived from Japanese astronomers' observations but deduced based on Captain A. J. Krusenstern's observations in Nagasaki and Tadataka Ino's land survey. The working value of the longitude of Kyoto adopted by Japanese astronomers of early nineteenth century was 135°55′45″, the value based on eclipse observations, and the value 135°40′ was never used for official astronomical purposes in Japan.
In the middle part of Shizuoka Prefecture many landslide cases are recognized widely spread in the rhythmic alterations of sandstone and clayslate, supposed to have come out in the age of Cretaceous. This is one of the reports, recording the details of the preventive work of landslide at Naka-kawane-Cho, Haibara-Gun. The core-boring method was taken to know the real condition of ground water directly and to get the concrete materials requisite for the preventive work. Boring was put as densely as possible and arranged it in the form of section paper. We planned to make the depth 50 m. at the slow slope and 20 m. at the steep slope. Sometimes we changed the depth case by case. Excess and deficiency was adjusted, changing the number of holes, thus with flexible and efficient method. We intended to find the real condition of weather rock, clayey part, crushed part and bed rock as possible. As a result, we found the landslide take place, being oppressed by clayey part, which is supposed to be sliding surface. Following are the methods we are taking for the drainage of ground water. 1. Well. 2. Horizontal bore hole. 3. Underdrainage tunnel.