The following paragraph illustrates this method of explanation:—­

The lower portions of stream valleys which have sunk below sea level are called drowned valleys.  The lower St. Lawrence is perhaps the greatest example of a drowned valley in the world, but many other rivers are in the same condition.  The old channel of the Hudson River may be traced upon the sea bottom about 125 miles beyond its present mouth, and its valley is drowned as far up as Troy, 150 miles.  The sea extends up the Delaware River to Trenton, and Chesapeake Bay with its many arms is the drowned valleys of the Susquehanna and its former tributaries.  Many of the most famous harbors in the world, as San Francisco Bay, Puget Sound, the estuaries of the Thames and the Mersey, and the Scottish firths, are drowned valleys.

—­Dryer:  Lessons in Physical Geography.

+Theme XCII.+—­Develop one of the following topic statements into an expository paragraph by use of examples:—­

1.  Weather depends to a great extent upon winds.

2.  Progress in civilization has been materially aided by the use of nails.

3.  Habit is formed by the repetition of the same act.

4.  Men become criminals by a gradual process.

5.  Men’s lives are affected by small things.

6.  Defeat often proves to be real success.

(Have you made your meaning clear?  Does your example really illustrate the topic statement?  Can you think of other illustrations?)

+166.  Exposition by Comparison or Contrast.+—­We can frequently make our explanations clear by comparing the subject under discussion with something that is already familiar to the reader.  In such a case we shall need to show in what respect the subject we are explaining is similar to or differs from that with which it is compared. (Section 48.) Though customary it is not necessary to compare the term under discussion with some well-known term.  In the example below the term socialism is probably no more familiar than the term anarchism.  Both are explained in the selection, and the explanations are made clearer by contrasting the one with the other.

Socialism, which is curiously confounded by the indiscriminating with Anarchism, is its exact opposite.  Anarchy is the doctrine that there should be no government control; Socialism—­that is, State Socialism—­is the doctrine that government should control everything.  State Socialism affirms that the state—­that is, the government—­should own all the tools and implements of industry, should direct all occupations, and should give to every man according to his need and require from every man according to his ability.  State Socialism points to the evils of overproduction in some fields and insufficient production in others, under our competitive system, and proposes to remedy these evils by assigning to government the duty of determining what shall be produced and what each worker