Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

DIAGRAM

Online Encyclopedia
Originally appearing in Volume V08, Page 147 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

DIAGRAM (Gr. Scaypaµµa, from &aypackcv, to See also:

mark out by lines, a figure See also:drawn in such a manner that the geometrical relations between the parts of the figure illustrate relations between other See also:objects. They may be classed according to the manner in which they are intended to be used, and also according to the See also:kind of See also:analogy which we recognize between the diagram and the thing represented. The diagrams in mathematical See also:treatises are intended to help the reader to follow the mathematical reasoning. The construction of the figure is defined in words so that even if no figure were drawn the reader could draw one for himself. The diagram is a See also:good one if those features which See also:form the subject of the proposition are clearly represented. Diagrams are also employed in an entirely different way—namely, for purposes of measurement. The plans and designs drawn by architects and See also:engineers are used to determine the value of certain real magnitudes by measuring certain distances on the diagram. For such purposes it is essential that the See also:drawing be as accurate as possible. We therefore class diagrams as diagrams of See also:illustration, which merely suggest certain relations to the mind of the spectator, and diagrams drawn to See also:scale, from which measurements are intended to be made. There are some diagrams or schemes, however, in which the form of the parts is of no importance, provided their connexions are )roperly shown. Of this kind are the diagrams of See also:electrical connexions, and those belonging to that See also:department of See also:geometry which treats of the degrees of cyclosis, periphraxy, linkedness and knottedness.

Diagrams purely Graphic and mixed Symbolic and Graphic.—Diagrams may also be classed either as purely graphical diagrams, in which no symbols are employed except letters or other marks to distinguish particular points of the diagrams, and mixed diagrams, in which certain magnitudes are represented, not by the magnitudes of parts of the diagram, but by symbols, such as See also:

numbers written on the diagram. Thus in a See also:map the height of places above the level of the See also:sea is often indicated by marking the number of feet above the sea at the corresponding places on the map. There is another method in which a See also:line called a See also:contour line is drawn through all the places in the map whose height above the sea is a certain number of feet, and the number of feet is written at some point or points of this line. By the use of a See also:series of contour lines, the height of a See also:great number of places can be indicated on a map by means of a small number of written symbols. Still this method is not a purely graphical method, but a partly symbolical method of expressing the third See also:dimension of objects on a diagram in two dimensions. In See also:order to See also:express completely by a purely graphical method the relations of magnitudes involving more than two variables, we must use more than one diagram. Thus in the arts of construction we use plans and elevations and sections through different planes, to specify the form of objects having three dimensions. In such systems of diagrams we have to indicate that a point in one diagram corresponds to a point in another diagram. This is generally done by marking the corresponding points in the different diagrams with the same See also:letter. If the diagrams are drawn on the same piece of See also:paper we may indicate corresponding points by drawing a line from one to the other, taking care that this line of See also:correspondence is so drawn that it cannot be mistaken for a real line in either diagram. (See GEOMETRY: Descriptive.) In the See also:stereoscope the two diagrams, by the combined use of which the form of bodies in three dimensions is recognized, are projections of the bodies taken from two points so near each other that, by viewing the two diagrams simultaneously, one with each See also:eye, we identify the corresponding points intuitively. The method in which we simultaneously contemplate two figures, and recognize a correspondence between certain points in the one figure and certain points in the other, is one of the most powerful and fertile methods hitherto known in See also:science.

Thus in pure geometry the theories of similar, reciprocal and inverse figures have led to many extensions of the science. It is sometimes spoken of as the method or principle of Duality.

End of Article: DIAGRAM

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
DIAGORAS 		[next]
DIAGRAM 2

Site © 2006 - Net Industries