Toward the Infinitesimal

Modern scientists have been able to study ever smaller particles of matter. Recently the pursuit of the infinitesimal reached a new vanishing point. An R.C.A. microphysicist developed an instrument which can analyze the atomic composition of a particle as small as a millionth of a billionth of a gram.

The inventor of this "electron microanalyzer" is a fledgling still in his late 20s, James Hillier, co-inventor of the electron microscope (TIME, Oct. 28, 1940). The general atomic composition of bacteria and viruses is well known--they are mostly carbon, nitrogen, hydrogen, oxygen. But under high electronic magnification (100,000 times), bacteria often reveal granules of previously undetected substances that are hard to identify. The granules are much too small to be analyzed by a spectroscope, the conventional instrument for the quick determination of atomic components.

Hillier's analyzer, like the electron microscope, does its job by bombarding a substance with electrons. It has an electron "needle" of extremely fine focus. Hillier first lines up his minute target (such as the head or tail of a virus) by means of the microscope, then needles it with an electron stream of some 50,000 volts. This dislodges electrons from the atoms in the target. Since the energy required to dislodge them varies with the kind of atoms present, the loss of energy in the bombarding electrons after they pass through the substance indicates the nature of the atoms on hand. Thus a loss of 298 volts identifies carbon atoms; 400 volts, nitrogen atoms, etc.

The full significance of the electron microanalyzer is not yet clear, but instruments opening new vistas into the infinitesimal have always led to practical results.

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