Which rhetorical device is used in this excerpt from "the extraordinary american" by g. k. chesterton? he was a lean brown man, having rather the look of a shabby tropical traveller, with a grey moustache and a lively and alert eye. but the most singular thing about him was that the front of his coat was covered with a multitude of shining metallic emblems made in the shape of stars and crescents. i was well accustomed by this time to americans adorning the lapels of their coats with little symbols of various societies; it is a part of the american passion for the ritual of comradeship. there is nothing that an american likes so much as to have a secret society and to make no secret of it. but in this case, if i may put it so, the rash of symbolism seemed to have broken out all over the man, in a fashion that indicated that the fever was far advanced.

Metaphor

Basically, a metaphor is figure of speech that likens two things that happen to be quite different for the sake of presenting a clearer image to readers.  What the author does is anticipate what readers will be familiar with and compare that something to what readers may not be too familiar with.  This also helps make content easier for readers to understand.  For instance, in this excerpt, because readers were not present to see just how much the pins were over the man, the author likens the pins to what most readers are probably familiar with—a rash.  Thus, the author is implying that if you know just how badly a rash can cover a person, then you can begin to comprehend just how rampant the pins were all over this person.

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).