in a brace of shakes meaning in English

立刻

But by and by , as said , this evening after sundown , the wind sitting in the west , biggish swollen clouds to be seen as the night increased and the weatherwise poring up at them and some sheet lightnings at first and after , past ten of the clock , one great stroke with a long thunder and in a brace of shakes all scamper pellmell within door for the smoking shower , the men making shelter for their straws with a clout or kerchief , womenfolk skipping off with kirtles catched up soon as the pour came
如前所述，日暮时，风起西空，夜幕降临后，出现大朵乌云，翻滚膨胀。喜观天象者咸望之：惟见一道道闪电，十时许，一声巨雷，伴以悠长轰鸣，骤雨若烟雾，众人仓皇遁往家中。暴雨乍下，男子即以布片或手帕遮草帽，女子则撩起裙裾，跳蹿而去。