  There are still debates on whether the observed zero energy peak in the
experiment by Stevan {\it et al.} [Science 346, 602(2014)] reveals the
existence of the long pursuing Majorana bound states (MBS). we propose that, by
mounting two scanning tunneling microscopic tips on top of the topological
superconducting chain and measure the transmission spectrum between these two
metallic tips, there are two kinds of characteristics on the spectrum that are
caused by MBS uniquely. One is symmetric peaks with respect to zero energy and
the other is $4\pi$ period caused by a nearby Josephson junction. The former
refers to the fact that MBS are composited by Majorana fermions which
distributed in the particle and hole subspaces equally. The latter is based on
the well known $4\pi$ period of Josephson effect in topological superconductor.
We think such two characteristics can be used as criteria to distinguish MBS
from other candidates, such as impurities, Kondo effect and traditional Andreev
bound states.
