Shortly after the outbreak of war in Europe in 1939, German espionage agent entered this country, presumably on a reconaissance mission for the Nazi government. He made several contacts in Washington, then began a tour of cities along the East Coast. Intensely curious about the visitor's purposes, the Federal Bureau of Investigation assigned one of its own agents, Robert Tonis, to follow him. The German boarded a train for Boston, and Tonis, according to plan, waited for him at South Station. But as soon as the train pulled in, the spy dashed into a taxi, sped up Memorial Drive, stopped at Harvard, and ran into one of the Houses on the Charles River. Although Tonis had been close behind he was unable to pick up the trail: the man seemed to have vanished. Sometime later, the F.B.I. learned that the German had eluded pursuit by slipping into Harvard's steam tunnels.

Tonis has been interested in the Tunnel ever since, and when he became Chief of the University Police in 1962, one of the first things he did was to study its route. Harvard's network of steam tunnels (or simply, the Tunnel) extends for about three miles. It lies beneath the sub-basements of University buildings and connects the Business School, the Houses, the Yard, the Law School, and the science laboratories with the Cambridge Electric Company's steam generating plant on Western Avenue, several blocks below Dunster House. Unlike the Central Kitchens food tunnels (which are closer to the surface and a separate system altogether), the steam tunnels are not used for transportation. Instead, they carry the University's main utility lines; steam pipes for heating nearly all of Harvard, power and telephone cables, even WHRB's transmission lines.

For most of its length the Tunnel is ten feet high, ten feet wide, well-lighted, and hot. It is accessible from the basements of many buildings and, in a few places, from the surface. Once inside the Tunnel one can easily get into many dormitories, museums, and lecture halls; for just this reason, doors into the Tunnel are kept locked at all times. The elusive German spy doubtless arranged for someone to leave one of these doors open and made his escape by coming up to the surface at some point well away from the river. (Tonis, incidentally, picked up his trail again some hours later.)

The first section of Tunnel was built in 1914, but it took years to construct the system that exists today. The line from Weld Hall in the Yard to Langdell Hall at the Law School, for example, was not completed until 1927. Before the Tunnel, each building had its own boiler to supply steam for heating radiator water and domestic water. Now, steam for almost the whole University comes from a single source.

The other day, at the invitation of Buildings and Grounds, a small party of students explored the underground world of Harvard. Our point of departure was the basement of Weld Hall, one of nine operating stations in the Tunnel system. There, we met the foreman of the Tunnel operating engineers, Mr. Floyd Kingsbury, who first showed us a map of the University in which were indicated the areas under the control of Buildings and Grounds. We noticed four large shaded areas and two small ones; Radcliffe, left unshaded, was clearly not part of things.

Mr. Kingsbury explained that the four shaded blocs are all served by the Tunnel but that one of them--the Business School and Soldiers Field area--is not yet fully integrated with the other three. These others are the "North Yard" (everything north of Kirkland Street), the "Main Yard" (everything between Kirkland Street and Massachusetts Avenue and the river). In each, distribution of steam is fully automatic. We found out that the two small shaded areas on the map are independent of the Tunnel but nonetheless under Buildings and Grounds administration. (One includes the Loeb Drama Center and part of the Radcliffe Yard along Appian Way; the other takes in the Harvard Observatory and Kittredge Hall.)

Mr. Kingsbury then suggested a preliminary trip through the Tunnel and gave us over to one of his engineers. Before we left, however, he surprised us with one statistic: 62 men, he told us, work full time in the Tunnel, keeping a 24-hour lookout for breakdowns.

Our guide, Mr. Harry Schofield, led us down a short stairway, through a glass door, into the Tunnel. "There it is," he said and pointed down a seemingly endless corridor illuminated by incandescent bulbs spaced along the ceiling. The most impressive feature of the Tunnel was its temperature. We had prepared for our expedition by dressing in summer clothing, but the blast of heat that hit us when we entered was unexpected. A thermometer on the wall registered 120 degrees, the highest reading on its scale. For most of our travels, the temperature ranged from this extreme down to a comparatively balmy low of 90. The sources of all this heat turned out to be three large pipes along the walls, two ten inches in diameter, one twelve inches. Though encased in heavy insulation, each radiated considerable heat for the simple reason that the live steam inside was over 400 degrees.

As we walked south toward Widener Library, Harry Schofield pointed out some of the Tunnel's sights. He first called out attention to the large expansion joints that occurred at regular intervals along the steam pipes. These, he explained, allow for horizontal expansion when steam is turned on; without them, the rigid metal pipes would buckle disastrously due to sudden increases in temperature. Because the joints are the most likely sites for leaks to develop, they must be inspected and maintained continuously, and are one of the main concerns of the Tunnel engineering force.

"The whole service system of Harvard is predominantly underground," Harry told us. To support his statement he indicated the power conduit (a metal pipe of modest size) and the telephone lines (several thick black cables). It seemed to us that the whole service system of Harvard was also quite vulnerable to sabotage: an agent provocateur loose in the Tunnel could easily paralyze the University preparatory to leading a junta against it. We asked Harry whether unauthorized persons might wander in. "Rarely," he answered. "Occasionally, an outside contractor working in the Tunnel leaves a door open by mistake and a curious undergraduate comes through, but we soon catch him." As he finished his sentence, the long corridor we had been in came to and end, and we found ourselves in a very large, noisy room filled with silver-painted pipes and tanks.

Harry told us we had reached the Widener Chamber, one of three large junctions in the system. We spent some time examining control panels and gauges before we discovered that the noise was due to an enormous fan unit. The Widener Chamber, we learned, is also a ventilation center, where stale air is pumped out of the Tunnel and fresh air sucked down from the surface. (Some of the intake air is compressed to operate control units in the heating system.) The exhaust outlet of the Widener Chamber gave us, at least, a chance to locate ourselves with reference to the surface topography: it was high above our heads and looked out of the ground just behind the Chinese stone dragon on the west side of Widener Library.

From the Widener Chamber the Tunnel strikes out in three directions. The shortest spur goes east under the basement of Widener, Houghton, and Lamont Libraries. A second arm (the one we had been in) runs north to Weld (where we had entered) and beyond to the Law School and science laboratories. The third section goes south to the Houses and the Business School. We followed this for a short distance--it looked just like the ear-her part of the Tunnel until we came to another smaller chamber. "Here," said Harry, "is our own underground railway." The "railway" is no more than a pulley-operated car with room enough for one person to lie flat on it. But it serves an important purpose: we had come to Massachusetts Avenue, where the Tunnel must squeeze between the top of the MTA subway tunnel and the street--a space of about three feet--; the only practical method of travel is lying flat in a pulley-operated railway car.

After we had tired of riding back and forth, a new difficulty occurred to us: how, we wondered, did the Tunnel get to the Business School? We could scarcely believe Harry's answer. The Tunnel, he told us, actually runs through the Weeks footbridge to the other side of the Charles. We resolved at once to make the trip, and urged Harry to lead us. But Harry was a Main Yard man, unauthorized to cross the Massachusetts Avenue border into the South Yard; in order to follow the Tunnel farther we would first have to clear our itinerary with Mr. Kingsbury. And so with high anticipation we retraced our steps to Weld Hall.