VI. EARTHQUAKES.

 It is doubtful if the Earth’s crust exceeds, or equals 1,000 miles in thickness. The outside is held from flying to pieces by the atmosphere, which is a sort of tire to the earth, while the inside is constantly pressing from effect of centrifugal force. These two factors must meet somewhere.

 

On the outside, near the ice belt, the water pressure gets the best of the inner forces and drives the waters into Symmes’s Hole. In the Earth the centrifugal force has advantage until reaching the surface; but if a big hole could be cut at the Equator through to the center, no doubt a man could jump into it in safety and cease to fall as he cushioned against centrifugal influence in his descent. Earthquakes are only the effects of internal pressure of water to get to the surface, at times bursting large reservoirs, producing tremblings, and at others with[39] great force throwing up hills and mountains from the tops of which the fountains of water burst forth¹. At other times they are produced by the contact of water with heated elements in volcanoes, creating the commotion² leading to the volcanic³ eruption⁴, the latter of which can only be produced by contact of fire and water.

 

It is believed that this is the complete and brief explanation of earthquake causes.

1 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

2 commotion   

n.骚动，动乱

参考例句：

• They made a commotion by yelling at each other in the theatre.他们在剧院里相互争吵，引起了一阵骚乱。
• Suddenly the whole street was in commotion.突然间，整条街道变得一片混乱。

3 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

4 eruption   

n.火山爆发；（战争等）爆发；（疾病等）发作

参考例句：

• The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
• The eruption of a volcano is spontaneous.火山的爆发是自发的。