3. Using Classification to Explain

Some subjects are so complex that they can easily overwhelm a read­er. In dealing with such subjects, writers need to organize their ma­terial to help them present it clearly. One technique for organizing complex material is classification. To classify is to group material on the basis of similarity.

When writers classify, they must first decide on a principle of choice. That is, they must first select a basis for their classification. In writing about essays, for example, the writers might choose to classify them according to their type. The basis for classification, then, would be type of writing, and some resulting groups would be narration, de­scription, and exposition. All the material that could be considered nar­rative essays would go together in one group. Similarly, descriptive essays would form a second group and expository essays a third.

The material itself usually provides a key to the best basis for classifi­cation. The subject often has aspects that form natural groups or cate­gories. The writer must be careful, however, that the basis selected is broad enough to be complete. The basis must apply to all the known material to be classified. For example, if the subject were animals of many different kinds, a classification based on the presence of either wings or fins would not be complete if the material included animals that have neither wings nor fins. These would not fit in any group according to the writer's principle of choice. A better basis of classification would be means of movement. All animals move in some way, using wings, fins, feet, or something else. They would all fit into a group under this sys­tem of classification.

Having found a principle of choice that is complete, the writer must then apply it consistently. All the groups into which the material is divided must come from the basis of classification. For instance, if the subject is myths and the basis for classification is their cultural origin, each group should contain myths coming from a single culture. These might be a group of Greek myths, one of Roman myths, and one of Norse myths. A group based on goddesses’ names would not be con­sistent with the principle of choice.

WORKING WITH THE MODEL

Read the following portion of an article dealing with the subject of volcanoes. Notice the basis for classification and the groups into which the material is classified.

The French geologist Professor A. Lacroix, who had made extensive studies at Mont Pelee following the tragic eruption in 1902, proposed a classification which recognized four types of eruptions: (a) Hawaiian, (b) Strombolian, (c) Vulcanian, and (d) Pelean.

Hawaiian Type

The Hawaiian type, represented by the volcanoes of the Hawaiian Islands, has abundant outpourings of basaltic lava in which the gases are liberated more or less quietly. Explosive eruptions are rare, but fountains of lava, projected by jets of escaping gas, may play at heights up to 1,0.00 feet and more. The product is basic lava with only minor amounts of cinder, and ash. The outpourings of lava develop flat lava domes, forming, as in the case of Mauna Loa, some of the largest mountains on earth.

Strombolian Type

Stromboli, a volcano in the Aeolian Islands off the coast of Sicily, is in a constant state of activity and since ancient times has been known as the "lighthouse of the Mediterranean." The eruptions of Stromboli consist of more or less regular explosions of moderate intensity, which throw out pasty, incandescent lava (scoria) accompanied by a white vapor cloud. The lava in the center crusts over lightly, and at intervals of about one-half hour the pent-up gases escape with mild explosions, hurling out clots of lava and fragments of the crust. Many of the fragments fall back into the crater to be blown out again, but others fall on the slope of the cone and roll into the sea.