Controlling Shifts in Paragraphs

Although the main tense in the following paragraph is past, the writer correctly shifts to present tense twice. Find these two verbs in present tense. If you encounter difficulty, try reading the paragraph aloud.

The Iroquois Indians of the Northeast regularly burned land to increase open space for agriculture. In fact, the early settlers of Boston found so few trees that they had to row out to the islands in the harbor to obtain fuel. Just how far north this practice extended is uncertain, but the Saco River in southern Maine appears to have been the original northern boundary of the agricultural clearings. Then, pressured by European settlement, the Iroquois extended their systematic burning far northward, even into the Maritime Provinces of Canada. (abridged from Hay and Farb, The Atlantic Shore)

Read the following paragraph through, and determine the main tense. Then reread it and circle the three verbs that shift incorrectly from the main tense.

For the past seven years, I have called myself a swimmer. Swimming, my one sport, provides a necessary outlet for my abundant energy. I have always drawn satisfaction from exertion, straining my muscles to their limits. I don't know why pushing forward in the water, as my muscles cried out in pain, sets off a booming cheer in my head. Many times when I rounded the turn for the last lap of a race, my complaining muscles want to downshift and idle to the finish. My mind, however, presses the pedal to the floor and yells, "FASTER!" The moment that I touched the wall my muscles relax; the pain subsides. I am pleased to have passed the point of conflict. (adapted from Brendon MacLean, "Harder!")

You will notice several shifts in tense in the following paragraph describing action in a fictional narrative. Find the six faulty shifts in tense.

In "The Use of Force" William Carlos Williams describes a struggle involving a doctor, two parents, and their young daughter. The doctor must obtain a throat culture from the girl, who was suspected of having diphtheria. This ordinarily simple task is hindered by the frightened and uncooperative patient, Mathilda Olson. Adding to the doctor's difficulties were the parents, who had to struggle with their own conflicting emotions. They want their daughter helped, but they did not trust the doctor to do the right thing. Sensitive to the parents' uncertainty, the doctor became more and more frustrated by Mathilda's resistance. Williams gives considerable attention to how each of the Olsons react, but it is clear that his main interest was in the doctor and his responses.(adapted from a student essay)