A Dutch book entitled Algemeene Aardrijksbeschrijving (General Geography) by Jacob de Gelder in 1803-1808, which was introduced into Tokugawa Japan, is found to be one of the crucial sources for Kyuri-tsu, 1836 by Hoashi Banri. This Dutch book covers related topics such as astronomy, meteorology, geology and natural geography, but not human geography. French physics developed by LaPlace, etc. is emphasized in this book: The "geography " at that time implied several subjects related to the earch. Translations or quotations from this Algemeene Aardrijksbeschrijving to Kyuri-tsu amount to a quater of the whole content.
Kiyotsugu Hirayama (1874-1943), who is renowned for his finding of families of asteroids in 1918, had two astronomical interests in addition to the family after his return home from U.S. (1915-1917): the explanation of gaps in the distribution of the mean motion of the asteroids, and the theory of stellar evolution including the origin of binary system and the origin of stellar energy and the mechanism of the periodic variable stars. Although it seemed as if his researches of stellar evolution originated in another interest different from asteroid-researches, certainly it's half-true, all these were interrelated, too. No one states this view. He approached these problems through celestial mechanics. Given resisting particles in the solar system, he considered theoretical effect of resistance on the motion of the asteroids in the librating region. And he speculated the capture theory of the stars that the cloud (mass of resisting particles) in the interstellar space can capture several stars passing through it. He said that his capture theory was naturally connected with the stellar evolution. In short, resisting particles (medium) was his key idea. His capture theory was an extension of the asteroid-researches under the resisting-medium hypothesis. But the theory not only was an extension of asteroid-researches, but also was caused by general interest shared with astronomers at the time. Finally, physical ground of his statement in 1933 that the outbreak of the asteroid families might have occurred after the medium had dissipated, was on his theory of solar system formation based on his capture theory.
At the outbreak of the Pacific War, the Japanese army was way behind in the development of radio weapons. Therefore, when they knew American and British forces had used radio weapons, the Japanese army held a research examination of radio weapons in the department of the army ordnance. This material introduced the report in the research. The report was mainly connected with radio weapons related to airplanes and showed detailed explanations about American, British, and German conditions with regard to radars, guardradars, and induce implements, and then it emphasized the importance of radio weapons in modern wars. And let me add that the Japanese army, based on this report. summoned scholars and students, for example, Dr.Okabe in Osaka University, and succeeded in completing radars and guardradars around the autumn in 1943.