Complex sentence: Having taken up the idea of quantitative mouth-blowpipe assaying, which was then almost unknown, he succeeded in devising dependable methods for all the ordinary useful metals; in particular his modes of assaying for nickel and cobalt quickly found favour with metallurgists.
Split into simpler sentences: Having taken up the idea of quantitative mouth-blowpipe assaying, which was then almost unknown. He succeeded in devising trustworthy methods for all the ordinary useful metals; in particular his modes of assaying for nickel and cobalt quickly found favour with metallurgists.