2 SOCIAL SCIENTIST thereby making much of the earlier data or inferences obsolete. Nevertheless we have gathered sufficient evidence to at least raise precise questions about the pace of innovation and diffusion of certain crucial technological devices. In the history of technology one moves with time from the simple to the complex. As archaeologists study the evolution of stone tools from the paleolithic to neolithic stages, they see progress essentially in terms of a proliferation of specialised types. Since in the present lecture I should like to confine myself to the modes of the harnessing and transmission of power, it is really from the late neolithic period, some seven thousand years ago, that our story begins. Human understanding of some of the elementary technological principles has often come exceedingly slowly. The wheel, such an important element in our technology, was not discovered by the Amcrindian portion of mankind, although they could build cities and monuments of a size that we must still admire. The initial rotary motion that led to the wheel came with the making of pottery, and with the discovery that its shape could be made more symmetrical through shaping the wet clay by hand through half rotations.6 From here the next step was the horizontal potter's wheel, a stage reached before B.C. 4000 at a chalcolithic community at Mehrgarh in the Kachhi plain below Quetta in Pakistan.7 With the finds at this site South Asia can claim precedence over Mesopotamia and Egypt in the use of wheel-turned pottery.8 But the potter's wheel did not necessarily lead to the vertical wheel or cart-wheel, which was perhaps the much more crucial invention. So far as our present evidence goes, this had to wait till the Indus culture, a thousand or more years later (B.C. 2800-1800, set by calibrated radio-carbon dates). Here miniature clay representations and traces of cart-ruts announce the arrival of the bullock-cart.9 The cart itself was very possibly a Mesopotamian invention, since evidence for the 'wagon* on solid wheels in Iraq goes back to the fourth millennium. B.C.10 The yoking of the ox to the cart should have raised immediately the question why it was not already yoked to the hoe so as to produce the plough. In Egypt the plough had, indeed, preceded the cart. And yet Kosambi strongly countered any suggestion that the plough could have been in use in Indus culture;11 and Gordon, while theorising on its presence, did not surprisingly make use of the argument that once animal traction was in use, the plough could not have been absent.12 The matter was settled with B.B. Lal*s important discovery of the furrowed field below Indus levels at Kalibangan in Rajasthan;13 and it has now been confirmed with the finding of toy clay ploughs at Banavali (Haryana).14 It may be marked that the Indian ox with its