Assertion: nebula | /r/CreatedBy | the length of the slit
Facets:
Source sentences:
text: When either of the four stars Alpha, Beta, Gamma, Delta Trapezii was brought upon the slit, a continous spectrum of considerable brightness, and nearly linear (the cylindrical lens of the apparatus having been removed), was seen, together with the bright lines of the nebula, which were of considerable length, corresponding to the length of the slit.