Utilization of Manpower
It is only too easy for historians to overlook the importance of muscle power during the 18th century. Horse whims and tread-wheels, despite their widespread use and importance in their day, have been overshadowed by more efficient and spectacular technologies like waterwheels, windmills, and steam engines. But an innovation does not immediately cause the abandonment of earlier, inferior technologies as obsolete. On the contrary, the total use of old technologies declines slowly and asymptotically. Treadwheels, for example, were used in Swedish mines as late as the 1880s, and one is even reported to have been in use as late as 1896. Muscle power was the dominant power technology during the 18th century: the total work produced by men, horses, and oxen in fields, roads, forests, mines, mills, and harbors probably exceeded the combined power of all steam engines, waterwheels, and windmills.
Industry needed sources of mechanical power capable of high output and continuous operation. The muscle power of men and animals
could provide continuous operation, but output was relatively low. A man working a ten-hour day produced approximately 0.1 horsepower, a horse in a good harness roughly six times as much. Horse whims used at the mines, driven by two or four horses, could thus develop approximately 1.2 or 2.4 horsepower. Continuous operation in three shifts required as many as a dozen horses. Perhaps eighty or even forty men could have produced an equivalent amount of work, but animals offered certain advantages when continuous power of this magnitude was required. In other cases, however, the power supplied by a few persons was not only sufficient but preferable—turning a crank or a windlass, pulling at ropes, carrying burdens, tramping in treadwheels. Compared to horses and oxen, men were relatively small and movable; their power output could be regulated with a word or a glance. The factor of control was significant when it came to loading or unloading ships, turning lathes, grinding and polishing, operating textile machines, or building.
Early attempts to determine how much physical labor a man could be expected to do in a day were made around 1700 at the Académie royale des sciences. Inquiries continued through the 18th century. Bernard Forest de Bélidor, Charles Augustin Coulomb, John T. Desaguliers, Johann Euler, and Philippe de La Hire were among those who addressed related questions of a fair day's work and the comparative strength of men and horses. No consensus was reached, but a large body of data was generated.
In these 18th-century studies, Eugene S. Ferguson has written, "the most casual and fragmentary data were being worked up, with the help of algebraic operations, into definite and precise conclusions." A case in point, described in more detail by Ferguson in an earlier paper, is a study published by Coulomb in 1798. On the basis of two single observations of physical labor, Coulomb wrote an equation for the useful work done while carrying one load of firewood upstairs. This equation was then differentiated and set equal to zero. Coulomb claimed to have obtained thereby the optimum load that would lead to the maximum day's work.
In an article published in 1744, the Swedish mathematician Pehr Elvius compared the efficiency of four treadmills then operating in Stockholm: one at the new Royal Palace under construction, one at a glass factory, and two at the construction of Stockholm's lock. For each treadmill, Elvius measured the rate at which a weight was raised and calculated that "the output of every single fellow is so great that 4 2/5 lispounds was hoisted at a rate of one foot every second." After discussing the differences in design and output for the four treadmills, he attempted to draw general conclusions concerning the ideal design for various applications.
Though Elvius recognized that quantitative methods could be used to improve an existing technology, his method suffered from two interdependent weaknesses, one mathematical and the other social. He used a single observation for each type of treadwheel ("a time of 4 minutes exactly or 240 seconds"), not an average value. Furthermore, his study was based on the types of treadwheels that could be seen in action in the course of a leisurely stroll through the
capital. But the large majority of treadwheels were at work in the mines of the countryside.
The opportunity for a systematic study of manpower did not arrive in Sweden until the early 1770s. The place was the naval dockyard of Karlskrona in the southeast, where manual labor was used to operate the pumps. To dry-dock a man-of-war, ninety sailors worked in three shifts of ten to thirteen hours depending on the displacement of the ship. The engineer Johan Eric Norberg studied the efficiency of manual labor during dry-docking on ten different occasions during 1772 and 1773, and published his report in the Proceedings of the Royal Swedish Academy of Sciences. His primary aim was to increase the efficiency of the pumping operation, but he also had in mind to determine in general the output that could be expected from human muscle power. This, Norberg wrote, had not been attempted before, save in a very small number of tests of limited scope. The results had fallen short in both reliability and extent. Norberg thus demonstrated his awareness that many tests under varying conditions were required to obtain results of general validity. Norberg took hundreds of measurements of the work of the ninety men. Figure 10.3, which shows one of his tables, illustrates the systematic nature of his approach.
Norberg's study is the earliest example in Swedish technology of a systematic, full-scale investigation intended to yield a result of general
applicability. It is scarcely surprising that Norberg chose the navy as the locus for his study. The military was the only social institution sufficient in size and authority to assemble and command the large work force needed for so ambitious a study of the efficiency of manual labor.
In his study in the 1740s Elvius had discussed the performance of only a few individuals. Even the physical characteristics of the individual—in particular, the length of his stride—was an important parameter in Elvius' calculation (dust jacket illustration). But in Norberg's study of the dockyard, individuals are reduced to figures in a table, and the combined product of ninety men's work expressed as a single quantity. Norberg was certainly aware of influential external factors: "harmony, the ration of spirits, the gentle persuasion of the officers, fair or foul weather, etc., have the most important influence on the work, and make a great difference as to output, which should otherwise be nearly the same for equal weights of water." These more human aspects of work at the pumps were not reproduced in Norberg's table, however, which expressed output as a product of measurable physical quantities. Norberg distinguished "the outputs of three kinds of people in various corps." In the sixth column of the table the letter V denotes volunteers (Volontairer ), M , marines (Marinierer ) and B , tenement seamen (Rote-Båtsmän ). The attempt to obtain average rather than individual values necessitated suppression of individual characteristics in favor of general traits.