这里的scacely和not是不是双重否定表示肯定

there is scarcely a thing which contributes to the welfare and comfort of humanity , scarcely an article of household furniture , a kitchen utensil , an article of clothing of food, that is not capable of an improvement in which there may be a fortune.

我觉得不能简单的认为是双重否定啥的，因为否定所在的成分不同。

an article of clothing of food, that is not capable of an improvement in which there may be a fortune.而且这个最后面的that的句子真的前面是逗号么？？？？？

有点不符合常理啊！！如果不是从句的话（逗号后面只能用which引导从句），那么一个句子出现了两个句子，并且中间没有连词连接······你从哪里找到的句子？