  The structural stratification of a solar-type main sequence star primarily
depends on its mass and chemical composition. The surface heavy element
abundances of the solar-type stars are reasonably well determined using
conventional spectroscopy, however the second most abundant element helium is
not. This is due to the fact that the envelope temperature of such stars is not
high enough to excite helium. Since the helium abundance of a star affects its
structure and subsequent evolution, the uncertainty in the helium abundance of
a star makes estimates of its global properties (mass, radius, age etc.)
uncertain as well. The detections of the signatures of the acoustic glitches
from the precisely measured stellar oscillation frequencies provide an indirect
way to estimate the envelope helium content. We use the glitch signature caused
by the ionization of helium to determine the envelope helium abundance of 38
stars in the {\it Kepler} seismic LEGACY sample. Our results confirm that
atomic diffusion does indeed take place in solar-type stars. We use the
measured surface abundances in combination with the settling predicted by the
stellar models to determine the initial abundances. The initial helium and
metal mass fractions have subsequently been used to get the preliminary
estimates of the primordial helium abundance, $Y_p = 0.244\pm0.019$, and the
galactic enrichment ratio, $\Delta Y / \Delta Z = 1.226\pm0.849$. Although the
current estimates have large errorbars due to the limited sample size, this
method holds great promises to determine these parameters precisely in the era
of upcoming space missions.
