Could anyone help me parse this sentence, please?

Question

At the time Malthus was writing, the world's population was under a billion, but the onset of the Industrial Revolution set in train a remarkable swelling of human numbers to more than 3 billion by the 1960s -- with no sign of any global Malthusian catastrophe.

In the above paragraph, I can't parse the sentence "but the onset of the Industrial Revolution set in train a remarkable swelling of human numbers to more than 3 billion by the 1960s". Which is the subject and which is the verb? And what does that sentence mean?

Answer 1

"The onset of the Industrial Revolution" is a noun phrase that functions as the subject of the sentence (the main noun here is "onset")

"Set in train" is a verbal phrase meaning "make (a process) start" see http://idioms.thefreedictionary.com/set+in+train. The use is metaphorical. A train is a line of cars joined together. If you set the first car moving, then all the others will follow. Thus the Industrial revolution resulted in a series of other events which eventually resulted in the population explosion.

It means "the Industrial revolution indirectly caused the human population to grow to 3 000 000 000 by the 1960s. This growth was remarkable."

Answer 2

At the time Malthus was writing, the world's population was under a billion, but the onset of the Industrial Revolution set in train a remarkable swelling of human numbers to more than 3 billion by the 1960s -- with no sign of any global Malthusian catastrophe.

At the time | Malthus was writing | the world's population was under a billion | but | the onset | of the Industrial Revolution | set | in train | a remarkable swelling | of human numbers | to more than 3 billion | by the 1960s | with no sign | of any global Malthusian catastrophe

This is a Compound Sentence. It is two sentences combined into one with a comma and a coordinating conjunction but.

I will italic the subject and bold the verb in each sentence.

At the time | Malthus was writing | the world's population was under a billion

but |

the onset | of the Industrial Revolution | set | in train | a remarkable swelling | of human numbers | to more than 3 billion | by the 1960s | with no sign | of any global Malthusian catastrophe

I guess at the time Malthus was upset and started writing about how there were too many people on the planet, a billion! He thought the world might end with so many mouths to feed and bodies to take care of, and the poor earth was being over taxed and if more people were born, it couldn't could handle the overburdening load. Little did he know, that long after his death, starting at the time of the origins of the Industrial Revolution, the the population would bloom to 3 billion. Now, look at where we are at--over 7 billion!