Some of the mourners saw in the dust visions from that deadly day when the very ground was on fire and the powder and smoke caked the living and the dead. 

=Some of the mourners saw visions in the dust from that deadly day when the very ground was on fire and the poweder and smoke caked the living and the dead

参考译文：有些哀悼者在尘土中看到了那个致命的日子的景象：大火就在这这块土地上燃烧，灰尘和烟雾落在活人和死人身上积结成块。

请问老师， 划线句子“when the very ground was on fire and the powder and smoke caked the living and the dead”是visions 的同位语从句吗？from that deadly day又作什么成份？

解答如下：

when the very ground was on fire and the powder and smoke caked the living and the dead. 为定语从句，修饰前面表示时间的名词that deadly day,