The emission line stars are peculiar objects
subject to photometric and spectroscopic variations.
From the spectroscopic
point of view this behaviour does not allow a rigorous classification
of the line intensity and shape of a given object,
on the basis of its belonging to a particular category.
In spite of this, or rather because of this problem, any extensive
description of the phenomenology of individual stars is important in
helping the interpretation of the physical reasons of the observed
behaviour, and for understanding the nature of the objects.
This is particularly true for the still poorly investigated near-infrared
region, which can now rather easily be observed with the currently used
spectrographs and detectors with good resolution and S/N.
As discussed here and in previous articles
(e.g. Baratta et al. 1991; Altamore et al. 1992;
Viotti et al. 1992; López et al. 1992)
the region around 1 
m includes important transitions of hydrogen,
neutral and ionized helium, and permitted and forbidden ionized iron
which can be used for the diagnostics of the geometry and physical
conditions in the circumstellar envelopes of mass losing stars and
interactive binaries.
Of particular interest is the Fe II 1.00 m line arising
from a level near the ionization limit, which might be populated
by dielectronic recombination or by fluorescence.
In many early-type emission line stars this line is in fact
very intense, with a strength frequently comparable to that of
the nearby P
(e.g. López et al. 1992).
Also the similarity of the profiles of the two lines in many targets
such as the classical Be star 
Cas studied here,
suggests that the Fe II line should be formed in the same region,
and can therefore be used to trace the stellar
H II envelope, with the advantage of being optically thin and
not affected by the photospheric absorption as in the case of the
nearby hydrogen line.
Acknowledgements
We thank the technical staff of Observatoire de Haute Provence for their valuable support during the observations. This research has made use of the Simbad database, operated at CDS, Strasbourg, France.