Scientific and surveying apparatus, and electrical apparatus and instruments for use therein; surveying and aligning apparatus for use in the construction industry; including laser beam projecgors, targets and transits therefor, grade determining devices, blowers, targets utilized with said projectors, surveying transits, apparatus for corrlating the alignment of said projectors with the sighyting of said transits, and apparatus for mounting all of the above components in a predetermined relationship to each other