We shall only refer to one more of these reliefs and that the one with which the series appears to close (Fig. 152). This carved picture has been thought, not without reason, to represent the erection of the bull[413] in its destined place. After its slow but uninterrupted march the huge monster has arrived upon the plateau where it has been awaited. By one great final effort it has been dragged up an inclined plane to the summit of the mound and has been set upon its feet. Nothing remains to be done but to pull and thrust it into its place against the doorway it has to guard and ornament. The same sledge, the same rollers, the same lever, the same precautions against accident are to be recognized here as in the last picture. The only difference is in the position of the statue itself. Standing upright like this it is much more liable to injury than when prone on its flank. New safeguards have therefore been introduced. It is packed under its belly with squares of wood and inclosed in scaffolding to prevent dangerous vibration. Additional precautions against this latter danger are provided by gangs of men who walk at each side and hold, some ropes fastened to the uprights of the scaffolding, others long forked poles engaged under its horizontal pieces. By these means equilibrium could be restored after any extra oscillation on the part of the sledge and its burden. All these manoeuvres are remarkable for the skill and prodigality with which human strength was employed; of all the scientific tools invented to economise effort and to shorten the duration of a task, the only one they seem ever to have used was the most simple of all, the lever, an instrument that must have been invented over and over again wherever men tried to lift masses of stone or wood from the ground. Its discovery must, in fact, have taken place long before the commencement of what we call civilization, although its theory was first expounded by the Greek mathematicians. [Illustration: FIG. 152.--Putting a bull in place; from Layard.] In a relief in the palace of Assurnazirpal at Nimroud, there is a pulley exactly similar to those often seen over a modern well.[414] A cord runs over it and supports a bucket. There is no evidence that the Assyrians employed such a contrivance for any purpose but the raising of water. We cannot say that they used it to lift heavy weights, but the fact that they understood its principle puts them slightly above the Egyptians as engineers. NOTES: [411] As to the simplicity of Egyptian engineering, see the _History of Art in Ancient Egypt_, vol. ii. p. 72, and fig. 43. [412] See LAYARD, _Monuments_, 2nd series, plate ii. The same author gives a detailed description of this picture in his _Discoveries_, pp. 104-106. [413] LAYARD, _Discoveries_, p. 112. [414] LAYARD, _Nineveh_, vol. ii. p. 32. Sec. 10.--_On the Graphic Processes Employed in the Representations of Buildings._