These are identical in form with present participles, for which they are frequently mistaken. The distinction, however, is clear, for the present participle is never used as the name of an action. Hence no such word in -ing that is a subject or an object, or stands in any other noun construction, can be a participle.

That nouns in -ing are real nouns may be proved by putting ordinary nouns in their place.

Travelling broadens the mind.Travel broadens the mind.
Talking is useless.Talk is useless.
He is afraid of falling.He is afraid of a fall.

348. From nearly every English verb there may be formed a verbal noun in -ing.

Verbal nouns in -ing have the form of present participles, but the construction of nouns.

They are often called participial nouns.

Such nouns are freely used, either by themselves or in a series along with ordinary nouns.

349. Verbal nouns in -ing have certain properties of the verb.