 Originally, the Martian war machines were supposed to walk on  visible electronic beams. This was attempted by having electrical  sparks emanate from the three holes at the bottom of the machine.  This was quickly abandoned for fear of it becoming a major fire  hazard. The first two shots of the first war machine emerging from  the gully has this effect. During filming, the actors were under the  impression that they were dealing with the walking tripod machines  of the book. This explains the farmhouse scene when  Gene Barry (qv) says, "Theres a machine standing right next to  us." However, the results of the walking can be seen wherever the  Martian machines fly throughout the film even though the sparking  effect was no longer used.