Paddle - Kai

A boat propulsion device. There are two types of paddles: paddles and oars. They are generally called "kai" (paddles are paddles), but in maritime history, paddles are called "kai" and oars are called "kai" (oars are paddles).

The appearance of oars as a means of propelling ships is extremely ancient, being clearly depicted in ancient Egyptian paintings from about 5,000 years ago. In these, the rowers face forward as they row, and the paddle has no fulcrum, which was probably the first method of propulsion devised by mankind. In contrast, oars, which have a fulcrum on the side of the ship and are rowed backwards, appeared slightly later than paddles. Not only were they superior in terms of mechanics, but they were also an essential propulsion device for large ships with high sides, and so they have dominated human-powered propulsion devices on a global scale, from ancient Greece and Rome to the present day.

In Japan, paddles were already in use on dugout canoes from the early Jomon period about 5,000 years ago, and this continued into the Yayoi period. The same was true in ancient China. The reason why the use of paddles spread so quickly across time and region is because paddles were the only type of boat that could be used on the narrow dugout canoes of ancient times. Just because Jomon oars are similar to those of ancient Egypt and Greece, we should not hastily conclude that this was due to the introduction of paddles.

On the other hand, the earliest definite evidence of the use of oars in Japan is a boat-shaped clay figurine excavated from the Saitobaru Tomb in Miyazaki Prefecture, dating back to the 5th century. This has six fulcrums for oars on each side of the boat. It is likely that this was introduced from the continent during the Yayoi period along with shipbuilding technology for large ships. This is because at the time in China, paddles were used for small boats and oars for large ships, and this is thought to have had a direct influence on the Yayoi and Kofun periods. Additionally, the "Manyoshu" features kaji and kai, and as the former is also described as "makaji shijinuki," it is reasonable to assume that they were oars for large ships and the latter were paddles. In the Heian period, better oars began to be used, and since then they have been the main propulsion device in Japan, while oars became used for some small boats such as tenmasen, but on the Japan Sea coast, oars were mainly used for large and small ships until the early modern period, and the spread of oars was delayed. There is also a type of oar called a neri oar, which is rowed in a similar way to a oar.

Since the Meiji period, modern warships and merchant ships have been propelled by steam engines, and the yachts they are equipped with, as well as racing boats such as fours and eights, and rental boats in parks, all use oars imported directly from Europe. Although functionally they are the same, they are unrelated to the traditional Japanese oars.

[Kenji Ishii]

"Illustrated History of Japanese Ships" by Kenji Ishii (1983, Shiseido)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

船の推進具。水をかいて生じる抵抗を利用して船を進める道具としての櫂には、パドルpaddleとオールoarがあり、一般に同音の「かい」でよばれるが、船舶史のほうではパドルを櫂、オールを橈(かい)と区別している。

　船の推進具としての櫂の出現はきわめて古く、約5000年前の古代エジプトの絵に明瞭(めいりょう)に描かれている。これは漕(こ)ぎ手が前を向いて漕いでおり、支点のないパドルであるが、この方法は初めて人類が考えた推進法であろう。これに対して、舷側(げんそく)に支点を設け、漕ぎ手が後ろ向きで漕ぐオールは、パドルよりやや遅れて現れた。これは単に力学的に優れているだけでなく、舷側の高い大型船用としては欠かせない推進具であったため、古代ギリシア、ローマから今日に至るまで世界的な規模で人力推進具の主流を占めることになった。

　日本の船では約5000年前、縄文時代前期の丸木舟にすでにパドルが使われ、それは弥生(やよい)時代にかけて変わりがない。古代の中国でも同様である。このようにパドルの使用が時代と地域を問わず早くから広まっているのは、古代の幅の狭い丸木舟ではパドルしか使えなかったためである。縄文期の櫂と古代エジプトやギリシアの櫂とが似ているからといって、これを伝播(でんぱ)によるものと速断すべきではないだろう。

　他方、日本でのオール使用のもっとも早い確証は、5世紀ごろの宮崎県西都原(さいとばる)古墳出土の船形埴輪(はにわ)である。これには左右の舷上に6個ずつのオール用の支点がある。これはおそらく弥生時代に大陸から大型船の造船技術とともに導入されたものと思われる。というのは、当時、中国では小舟にはパドル、大型船にはオールを使っているためで、これが弥生時代、古墳時代にも直接的な影響を与えたとみられる。また『万葉集』にはカヂとカイが登場するが、前者は「真楫繁貫(まかじしじぬ)き」ともあることから大型船用のオール、後者はパドルと解するのが妥当であろう。平安時代になると、より優れた櫓(ろ)が使われ始め、以来これが日本の推進具の主流となり、橈は伝馬船(てんません)など一部の小舟用となったが、日本海側では近世前期まで大小の船に橈が主用され、櫓の普及は遅れた。なお櫂には、練り櫂といって櫓と似た漕ぎ方をするものもある。

　明治時代以後の近代的な軍艦や商船は蒸気機関のプロペラ推進にかわり、それに搭載される端艇(たんてい)のほか、競技用ボートのフォア、エイトなどや公園の貸ボートなどにはすべてヨーロッパ直輸入のオールが使われるようになった。これらは機能的には同じオールであるが、日本古来のものとは無関係である。

［石井謙治］

『石井謙治著『図説和船史話』（1983・至誠堂）』

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