!) Instituto Argentino de Radioastronomía, CC5, Villa Elisa ( 1894 ),

Provincia de Buenos Aires, Argentina.

2) Member of the Carrera del Investigador Científico y Tecnológico of CONICET,

from Argentina.

3) University of Puerto Rico, Department of Physics and Electronics, Humacao

University College, HUC Station, PR00791, Puerto Rico.

High quality, sensitive observations of the H166 alpha recombination line were made with the 43m antenna of the National Radio Astronomy Observatory ( NRAO ), in Green Bank, West Virginia, United States of America. The results of the observations in the galactic longitude range 60º < l < 90º at each degree in galactic longitude and galactic latitudes b=0.0o, b=+0.5º, b=+1.5º, b=-0.5º, b=-1.5º, together with observations at l=81º and l=83º for b=-4º to b=+5º, each degree in galactid latitude, clearly show more recombination line emission for positive galactic latitudes than for negative galactic latitudes. We interpret these results as an strong evidence of the warp of the low density ionized gas layer, traced by the H166 alpha emission, towards positive latitudes in the Northern Galactic Plane.

An evidence of the warp of the ionized gas layer towards negative latitudes had been previously obtained from less sensitive H166alpha observations in the Southern Galaxy ( Azcárate et al, 1990, RMAA, 20,75 ).