Diversified conglomerates were long a fixture of the U.S. stock market landscape, with the Dow industrials bolstered by big names such as 3M, General Electric, United Technologies and others. But many of those companies have since broken apart,

In early trading, the industrial conglomerate’s stock hit $242.77, for a gain of almost 8%, after activist investor Elliott Investment Management disclosed a $5 billion stake in the company. Shares closed up 3.