CHAPTER II. MECHANICAL ENGINEERING.

This work, as already explained, is to be devoted¹ to mechanical engineering, and in view of the difference of opinion that exists as to what mechanical engineering comprehends, and the different sense in which the term is applied², it will be proper to explain what is meant by it here.

I am not aware that any one has defined what constitutes civil engineering, or mechanical engineering, as distinguished³ one from the other, nor is it assumed to fix any standard here [14] farther than to serve the purpose of explaining the sense in which the terms will be used; yet there seems to be a clear line of distinction, which, if it does not agree with popular use of the terms, at least seems to be furnished by the nature of the business itself. It will therefore be assumed that mechanical engineering relates to dynamic forces and works that involve machine motion, and comprehends the conditions of machine action, such as torsional, centrifugal, intermittent⁴, and irregular strains in machinery⁵, arising out of motion; the endurance of wearing surfaces, the constructive⁶ processes of machine-making and machine effect in the conversion⁷ of material—in short, agents for converting, transmitting, and applying power.

Civil engineering, when spoken of, will be assumed as referring to works that do not involve machine motion, nor the use of power, but deal with static forces, the strength, nature, and disposition⁸ of material under constant strains, or under measured strains, the durability⁹ and resistance of material, the construction of bridges, factories, roads, docks, canals, dams, and so on; also, levelling and surveying. This corresponds to the most common use of the term civil engineering in America, but differs greatly from its application in Europe, where civil engineering is understood as including machine construction, and where the term engineering is applied to ordinary manufacturing processes.

Civil engineering, in the meaning assumed for the term, has become almost a pure mathematical science. Constants are proved and established for nearly every computation; the strength and durability of materials, from long and repeated tests, has come to be well understood; and as in the case of machine tools, the uniformity of practice among civil engineers, and the perfection of their works, attest¹⁰ how far civil engineering has become a true science, and proves that the principles involved in the construction of permanent works are well understood.

To estimate how much is yet to be learned in mechanical engineering, we have only to apply the same test, and when we contrast the great variance¹¹ between the designs of machines and the diversity of their operation, even when applied to similar purposes, their imperfection is at once apparent. It must, however, be considered that if the rules of construction were uniform, and the principles of machine operation as well understood as the strength and arrangement of material in permanent structures, still there would remain the difficulty of adaptation to new [15] processes, which are continually being developed.

If the steam-engine, for instance, had forty years ago been brought to such a state of improvement as to be constructed with standard proportions and arrangement for stationary¹² purposes, all the rules, constants, and data of whatever kind that had been collected and proved, would have been but of little use in adapting steam-engines to railways and the purposes of navigation.

Mechanical engineering has by the force of circumstances been divided up into branches relating to engineering tools, railway machinery, marine¹³ engines, and so on; either branch of which constitutes a profession within itself. Most thorough study will be required to master general principles, and then a further effort to acquire proficiency¹⁴ in some special branch, without which there is but little chance of success at the present day.

To master the various details of machine manufacture, including draughting, founding, forging, and fitting, is of itself a work equal to most professional pursuits, to say nothing of manual skill; and when we come to add machine functions and their application, generating and transmitting power, with other things that will necessarily be included in practice, the task assumes proportions that makes it appear a hopeless one. Besides, the work of keeping progress with the mechanic arts calls for a continual accretion¹⁵ of knowledge; and it is no small labour to keep informed of the continual changes and improvements that are going on in all parts of the world, which may at any time modify and change both machines and processes. But few men, even under the most favourable¹⁶ conditions, have been able to qualify themselves as competent mechanical engineers sooner than at forty years of age.

One of the earliest cares of an apprentice¹⁷ should be to divest¹⁸ his mind of what I will call the romance of mechanical engineering, almost inseparable from such views as are often acquired in technological¹⁹ schools. He must remember that it is not a science he is studying, and that mathematics deal only with one branch of what is to be learned. Special knowledge, or what does not come within the scope of general principles, must be gained in a most practical way, at the expense of hard work, bruised²⁰ fingers, and a disregard of much that the world calls gentility.

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Looking ahead into the future, the apprentice can see a field for the mechanical engineer widening on every side. As the construction of permanent works becomes more settled and uniform, the application of power becomes more diversified²¹, and develops problems of greater intricacy. No sooner has some great improvement, like railway and steam navigation, settled into system and regularity²² than new enterprises begin. To offset²³ the undertaking²⁴ of so great a work as the study of mechanical engineering, there is the very important advantage of the exclusiveness of the calling—a condition that arises out of its difficulties. If there is a great deal to learn, there is also much to be gained in learning it. It is seldom, indeed, that an efficient mechanical engineer fails to command a place of trust and honour, or to accumulate a competency by means of his calling.

If a civil engineer is wanted to survey railways, construct docks, bridges, buildings, or permanent works of any kind, there are scores of men ready for the place, and qualified²⁵ to discharge the duties; but if an engineer is wanted to design and construct machinery, such a person is not easy to be found, and if found, there remains²⁶ that important question of competency; for the work is not like that of constructing permanent works, where several men may and will perform the undertaking very much in the same manner, and perhaps equally well. In the construction of machinery it is different; the success will be directly as the capacity of the engineer, who will have but few precedents²⁷, and still fewer principles, to guide him, and generally has to set out by relying mainly upon his special knowledge of the operation and application of such machines as he has to construct.

(1.) How may mechanical be distinguished from civil engineering?—(2.) What test can be applied to determine the progress made in any branch of engineering?—(3.) What are some of the conditions which prevent the use of constants in machine construction?—(4.) Is mechanical engineering likely to become more exact and scientific?—(5.) Name some of the principal branches of mechanical engineering.—(6.) Which is the most extensive and important?

1 devoted   

adj.忠诚的，忠实的，热心的，献身于...的

参考例句：

• He devoted his life to the educational cause of the motherland.他为祖国的教育事业贡献了一生。
• We devoted a lengthy and full discussion to this topic.我们对这个题目进行了长时间的充分讨论。

2 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

3 distinguished   

adj.卓越的，杰出的，著名的

参考例句：

• Elephants are distinguished from other animals by their long noses.大象以其长长的鼻子显示出与其他动物的不同。
• A banquet was given in honor of the distinguished guests.宴会是为了向贵宾们致敬而举行的。

4 intermittent   

adj.间歇的，断断续续的

参考例句：

• Did you hear the intermittent sound outside?你听见外面时断时续的声音了吗？
• In the daytime intermittent rains freshened all the earth.白天里，时断时续地下着雨，使整个大地都生气勃勃了。

5 machinery   

n.(总称)机械，机器；机构

参考例句：

• Has the machinery been put up ready for the broadcast?广播器材安装完毕了吗？
• Machinery ought to be well maintained all the time.机器应该随时注意维护。

6 constructive   

adj.建设的，建设性的

参考例句：

• We welcome constructive criticism.我们乐意接受有建设性的批评。
• He is beginning to deal with his anger in a constructive way.他开始用建设性的方法处理自己的怒气。

7 conversion   

n.转化，转换，转变

参考例句：

• He underwent quite a conversion.他彻底变了。
• Waste conversion is a part of the production process.废物处理是生产过程的一个组成部分。

8 disposition   

n.性情，性格；意向，倾向；排列，部署

参考例句：

• He has made a good disposition of his property.他已对财产作了妥善处理。
• He has a cheerful disposition.他性情开朗。

9 durability   

n.经久性，耐用性

参考例句：

• Nylons have the virtue of durability.尼龙丝袜有耐穿的优点。

10 attest   

vt.证明，证实；表明

参考例句：

• I can attest to the absolute truth of his statement. 我可以证实他的话是千真万确的。
• These ruins sufficiently attest the former grandeur of the place. 这些遗迹充分证明此处昔日的宏伟。

11 variance   

n.矛盾，不同

参考例句：

• The question of woman suffrage sets them at variance. 妇女参政的问题使他们发生争执。
• It is unnatural for brothers to be at variance. 兄弟之间不睦是不近人情的。

12 stationary   

adj.固定的，静止不动的

参考例句：

• A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
• Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。

13 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

14 proficiency   

n.精通，熟练，精练

参考例句：

• He plied his trade and gained proficiency in it.他勤习手艺，技术渐渐达到了十分娴熟的地步。
• How do you think of your proficiency in written and spoken English?你认为你的书面英语和口语熟练程度如何？

15 accretion   

n.自然的增长，增加物

参考例句：

• Every culture is an accretion.每一种文化都是长期积淀的结果。
• An accretion of sediment at the mouth of the river caused serious flooding.河口堆积物的增加导致河水严重泛滥。

16 favourable   

adj.赞成的，称赞的，有利的，良好的，顺利的

参考例句：

• The company will lend you money on very favourable terms.这家公司将以非常优惠的条件借钱给你。
• We found that most people are favourable to the idea.我们发现大多数人同意这个意见。

17 apprentice   

n.学徒，徒弟

参考例句：

• My son is an apprentice in a furniture maker's workshop.我的儿子在一家家具厂做学徒。
• The apprentice is not yet out of his time.这徒工还没有出徒。

18 divest   

v.脱去，剥除

参考例句：

• I cannot divest myself of the idea.我无法消除那个念头。
• He attempted to divest himself of all responsibilities for the decision.他力图摆脱掉作出该项决定的一切责任。

19 technological   

adj.技术的；工艺的

参考例句：

• A successful company must keep up with the pace of technological change.一家成功的公司必须得跟上技术变革的步伐。
• Today,the pace of life is increasing with technological advancements.当今， 随着科技进步，生活节奏不断增快。

20 bruised   

[医]青肿的，瘀紫的

参考例句：

• his bruised and bloodied nose 他沾满血的青肿的鼻子
• She had slipped and badly bruised her face. 她滑了一跤，摔得鼻青脸肿。

21 diversified   

adj.多样化的，多种经营的v.使多样化，多样化( diversify的过去式和过去分词 )；进入新的商业领域

参考例句：

• The college biology department has diversified by adding new courses in biotechnology. 该学院生物系通过增加生物技术方面的新课程而变得多样化。 来自《简明英汉词典》
• Take grain as the key link, develop a diversified economy and ensure an all-round development. 以粮为纲，多种经营，全面发展。 来自《现代汉英综合大词典》

22 regularity   

n.规律性，规则性；匀称，整齐

参考例句：

• The idea is to maintain the regularity of the heartbeat.问题就是要维持心跳的规律性。
• He exercised with a regularity that amazed us.他锻炼的规律程度令我们非常惊讶。

23 offset   

n.分支，补偿；v.抵消，补偿

参考例句：

• Their wage increases would be offset by higher prices.他们增加的工资会被物价上涨所抵消。
• He put up his prices to offset the increased cost of materials.他提高了售价以补偿材料成本的增加。

24 undertaking   

n.保证，许诺，事业

参考例句：

• He gave her an undertaking that he would pay the money back with in a year.他向她做了一年内还钱的保证。
• He is too timid to venture upon an undertaking.他太胆小，不敢从事任何事业。

25 qualified   

adj.合格的，有资格的，胜任的，有限制的

参考例句：

• He is qualified as a complete man of letters.他有资格当真正的文学家。
• We must note that we still lack qualified specialists.我们必须看到我们还缺乏有资质的专家。

26 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

27 precedents   

引用单元； 范例( precedent的名词复数 )； 先前出现的事例； 前例； 先例

参考例句：

• There is no lack of precedents in this connection. 不乏先例。
• He copied after bad precedents. 他仿效恶例。