这里的 various 不是形容词，而是用作代词。

《新牛津英汉双解大词典》有如下例句：

[as pronoun] Various of her friends had called. 她的许多朋友都打来过电话。

但《新牛津英汉双解大词典》同时指出：

In standard English the word various is normally used as an adjective and determiner. It is sometimes also used as a pronoun followed by of, as in various of her friends had called. Although this pronoun use is similar to that of words such as several and many (e.g several of her friends had called) it is sometimes regarded as incorrect.