constructed of a nonmagnetic material disposed in parallel adjacent relationship thereto it is preferred that the guides 60 be constructed of aluminum and are attached to the soft steel side members by any suitable means such as rivets not shown for ease of understanding in fig5 one guide 60 is shown in cutaway view and the other is not the guides 60 serve two functions first each guide 60 contains an opening 64 adjacent each position to be occupied by a galvanometer motor the openings 64 are rectangular and sized to accommodate the magnets to be employed as will be hereinafter discussed in greater detail as a second function each guide 60 is adapted to position a galvanometer when it is inserted into the frame 52 this is best accomplished in the manner shown as by curving the ends of guides 60 inwardly at the point designated 66 in fig5 and cutting a slot therein through which the galvanometer support card to be described hereinafter can pass the design of the present galvanometer assembly is made possible by the recent development of rare earth cobalt magnets in particular a tested embodiment of the present invention employs samarium cobalt magnets the samarium cobalt magnets employed are one quarter inch thick of rectangular shape 1 2 u00d7 11 2 inches and have a sufficiently high intrinsic coercivity that they can maintain a.