When Annie Sullivan gives Helen some cake near the beginning of the film for spelling 'cake', the cake is so dry it literally blows out of Helen's mouth as she coughs on it!
"I'd say this cloud is Cumulo Nimbus."
"Didn't he discover America?"
"Penfold, shush."
It probably was a type of pound cake because they "travel well". Depending on the way it's prepared and the age of the cake, it could be rather dried out. Today's supermoist cakes weren't quite what cooks went for in "olden days", or maybe they were difficult to prepare without special cake flour. Into the Fifties and Sixties, the average cake was on the solid side. At least, that was the preference in this region and how I would judge cakes I've seen sliced and served in movies.
~~MystMoonstruck~~