Strong and Gentle Shetlands
When is a horse a pony？
Horses are measured in hands：one hand equals 4 inches．The height of a horse is measured from the ground to the highest point of the withers（the part of a horse，s back between its shoulder blades）．Any horse under 14 hands 2 inches（58inches）is a pony．
By this definition，a baby horse is not a pony；baby horses are called foals．Horses that do not develop to roughly the same size as the rest of their breed are not ponies either．Underdeveloped horses are called runts．
There are more than twenty breeds of ponies in the world．The bestknown are the Shetlands，the smallest of all breeds，which average a little less than 10 hands，about 39 inches．
Shetlands were first used in England as work animals in coal mines，because they were strong．They are also gentle，and may be trained to be good pets．
壮实、温顺的设得兰矮种马
什么时候一匹马算是矮马呢？
马是用手来测量的：一手掌之宽相当于4英寸。马的高度可从地面到马肩隆（马背上两个肩胛骨之间的部分）最高处的距离计量。凡低于14手掌2英寸（58英寸）的马，都是矮马。
根据这一定义，一匹幼马并不是矮马，幼马被称作驹。发育不良、未长到与同种马一般大小的马也不称矮马。发育不全的马被称作小种马。
世界上有20多个品种的矮种马。最着名的是设得兰种，是所有矮马中体形最小的一种，其平均高度略低于10手掌，约39英寸。
在英国，设得兰矮马最初在煤矿上充作力畜，因为它们长得壮实。它们也很温顺，可以训练为很好的玩赏动物。
The AirCushioned Vehicle That Travels Clear Out of Sea and Land
The aircushioned vehicle is not an airplane，since it does not have wings．It is neither a ship nor an automobile，since it travels clear of sea and land．It has a conventional gasoline engine，but no wheels．How does it travel？What keeps it in the air？
Under the air car is an air chamber with a large propeller parallel to the ground．The gasoline engine supplies power that causes the propeller to whirl．This fills the chamber with air．Some of the air is forced toward the ground through tiny holes around the edges of the car．
These air jets create a wall that keeps the air from escaping from the chamber．As more and more air crowds into the chamber，the molecules of air become compressed．Their pressure becomes so strong that it lifts the car off the ground．
Once the car is floating，the driver releases some of the compressed air．This makes the car speed forward．
脱离海面和陆地行驶的气垫船
气垫船不是飞机，因为它没有双翼。它不是轮船，也不是汽车，因为它脱离海面和陆地行驶。气垫船装有常规的汽油发动机，但没有轮子。它是怎样行驶的呢？是什么使它悬在空中的呢？
气垫船下面是一个空气箱，里面装有一个与地面平行的大螺旋桨。汽油发动机供能后，螺旋桨便旋转起来，这就使气箱内充满了空气。部分空气通过气垫船边缘的小孔被压向地面。
这些喷射出的气流形成一道屏障，阻止空气从气箱逸出。由于越来越多的空气聚集在气箱内，空气分子受到压缩。正是这些空气分子的强大压力使汽垫船脱离地面。
当气垫船浮动时，司机释放出一部分压缩空气，使气垫船高速向前飞行。
The American Museum of Natural History
When an art museum wants a new exhibit，it buys things in finished form and hangs them on its walls．When a natural history museum wants an exhibit，it often must build it realistically-from a mass of material and evidence brought together by careful research．
An animal，for example，must first be skinned．Photographs and measurements are used to determine the animal，s structure in a natural position-fighting，resting，or feeding．Then muscle forms are built and a plaster shell is made．Finally the skin is pulled over the shell like a wet glove．This completes the animal subject．
Displaying such things as stone heads，giant trees，and meteorites is basically mechanical．Most other natural history exhibits present more difficult problems．For instance，how can a creature be exhibited when it is too small to be seen clearly？In these cases，largerthanlife models are built．The American Museum of Natural History has models of fleas，houseflies，and a myriad other insects enlarged up to seventyfour times．The models show the stages of the insects， development and the workings of their bodies．
美国自然史博物馆
当一个艺术博物馆需要举办新展览时，馆方往往购买精美的成品，然后将它们挂在墙上。当一个自然史博物馆需要办展览时，工作人员却往往得通过认真的研究工作，获得大量的资料和实据，从而造出一件活生生的展品来。
例如，一只动物必须先剥其皮，再利用照片和测量法确定该动物在一种自然姿势中——斗殴、休息或进食的形态。然后造出肌肉模型，做好石膏外壳。最后将皮肤像湿手套一样罩在外壳上。这才完成了那件动物展品。
