By using 3 different crystallog. cuts of ferroelec. orthorhombic single domain samples of Ni-Cl boracite, 7 components out of the linear magnetoelec. tensor (aij) were measured. Among these 7 components, 2 nondiagonal ones were found nonzero though with different behavior below and above a crit. temp. of 9 DegK. The effect disappears entirely at .apprx.25 DegK. At 4.5 DegK the magnetoelec. coeffs. are |a23| ~ |a32| = (3.3 +- 0.4).10-12[sec/m]. At 8.5 DegK, a32 reaches a peak with twice that value. The measurements suggest the occurrence of magnetic phase transitions at 9 and 25 DegK.