A complex sentence may be expanded either by compounding the main clause or by increasing the number of subordinate clauses. Both methods may be used in the same sentence.
The independent main clause of a complex sentence may be compound.
When they saw the ship, they shouted for joy and some of them burst into tears.
As they turned down from the knoll to rejoin their comrades, the sun dipped and disappeared and the woods fell instantly into the gravity and grayness of the early night.—STEVENSON
The eye of the young monarch kindled and his dark cheek flushed with sudden anger, as he listened to proposals so humiliating.—PRESCOTT
Sharpe was so hated in Scotland during his life, and his death won him so many friends, or pitying observers, that it is not easy to write of him without prejudice or favor.—A. LANG
As has been the case with many another good fellow of his nation, his life was tracked and his substance wasted by crowds of hungry beggars and lazy dependents.—THACKERAY
Note that the subordinate clause depends on the compound main clause, not upon either of its members.
Thus, in the first example, the subordinate clause (when they saw the ship) depends upon the compound main clause, they shouted for joy and some of them burst into tears. It is an adverbial modifier of both shouted and burst.
Though a complex sentence can have but one (simple or compound) main clause, there is, in theory, no limit to the number of subordinate clauses.
Subordinate clauses may be attached to the main clause
(1) as separate modifiers or complements
(2) in a coordinate series of clauses, all in the same construction and forming one compound clause
(3) in a series of successively subordinate clauses, forming one complex clause.
Two or more subordinate clauses may be attached to the main clause separately, each as a distinct modifier or complement.
The bridge, which had been weakened by the ice, fell with a crash while the locomotive was crossing it. [The first subordinate clause is an adjective modifier of bridge; the second is an adverbial modifier of fell.]
The architect who drew the plans says that the house will cost ten thousand dollars. [The first subordinate clause is an adjective modifier of architect; the second is a complement, being the object of says.]
Isabella, whom every incident was sufficient to dismay, hesitated whether she should proceed. H. WALPOLE
As the boat drew nearer to the city, the coast which the traveller had just left sank behind him into one long, low, sad-colored line.—RUSKIN.
Those dangers which, in the vigor of youth, we had learned to despise, assume new terrors as we grow old.—GOLDSMITH.
When Farmer Oak smiled, the corners of his mouth spread till they were within an unimportant distance of his ears.—HARDY.
As Florian Deleal walked, one hot afternoon, he overtook by the wayside a poor aged man, and, as he seemed weary with the road, helped him on with the burden which he carried, a certain distance.—PATER.
While Joe was absent on this errand, the elder Willet and his three companions continued to smoke with profound gravity and in a deep silence, each having his eyes fixed on a huge copper boiler that was suspended over the fire.—DICKENS.
Two or more subordinate clauses in the same construction, forming one compound clause, may be attached to the main clause as a modifier or complement.
1. The truth was that Leonard had overslept, that he had missed the train, and that he had failed to keep his appointment.
2. The guide told us that the road was impassable, that the river was in flood, and that the bridge had been swept away.
3. Ellis, whose pockets were empty and whose courage was at a low ebb, stared dismally at the passing crowd.
4. Before the battle was over and while the result was still in doubt, the general ordered a retreat.
5. After we had arrived at the hotel, but before we had engaged our rooms, we received an invitation to stay at the castle.
6. My first thought was, that all was lost, and that my only chance for executing a retreat was to sacrifice my baggage.—DE QUINCEY.
7. The author fully convinced his readers that they were a race of cowards and scoundrels, that nothing could save them, that they were on the point of being enslaved by their enemies, and that they richly deserved their fate.—MACAULAY.
In the first and second examples, three coördinate noun clauses are joined to make one compound clause, which is used as a complement,—as a predicate nominative in the first sentence, as the direct object of told in the second.
In the third example, a compound adjective clause modifies Ellis. In the fourth and fifth, a compound adverbial clause modifies the predicate verb (ordered, received). In the seventh, four that-clauses unite in one compound clause.
Two or more successively subordinate clauses, forming one complex clause, may be joined to the main clause as a modifier or complement.
In such a series, the first subordinate clause is attached directly to the main clause, the second is subordinate to the first, the third to the second, and so on in succession.
In the course of my travels, I met a good-natured old gentleman, (a) who was born in the village (b) where my parents lived (c) before they came to America.
Here gentleman (a complement in the main clause) is modified by the adjective clause who was born in the village (a). Village, in clause a, is modified by the adjective clause where my parents lived (b). Lived, the predicate verb of clause b, is modified by the adverbial clause before they came to America (c).
Thus it appears that a is subordinate to the main clause, and that b, in turn, is subordinate to a, and c to b. In other words, the three clauses (a, b, c) are united to make one complex clause,—who was born in the village where my parents lived before they came to America. This clause, taken as a whole, serves as an adjective modifier describing gentleman.
Further examples of the successive subordination of one clause to another may be seen in the following sentences.
I have passed my latter years in this city, where I am frequently seen in public places, though there are not above half-a-dozen of my select friends that know me.—ADDISON.
In this manner they advanced by moonlight till they came within view of the two towering rocks that form a kind of portal to the valley, at the extremity of which rose the vast ruins of Istakar.—BECKFORD
The young fellow uttered this with an accent and a look so perfectly in tune to a feeling heart, that I instantly made a vow I would give him a four-and-twenty sous piece, when I got to Marseilles.—STERNE. [The conjunction that is omitted before I would.]
Three years had scarcely elapsed before the sons of Constantine seemed impatient to convince mankind that they were incapable of contenting themselves with the dominions which they were unqualified to govern.—GIBBON.
Mr. Lewis sent me an account of Dr. Arbuthnot’s illness, which is a very sensible affliction to me, who, by living so long out of the world, have lost that hardness of heart contracted by years and general conversation.—SWIFT.
NOTE : The method of forming complex clauses by successive subordination, if overworked, produces long, straggling, shapeless sentences, as in the following example from Borrow….
I scouted the idea that Slingsby would have stolen this blacksmith’s gear; for I had the highest opinion of his honesty, which opinion I still retain at the present day, which is upwards of twenty years from the time of which I am speaking, during the whole of which period I have neither seen the poor fellow nor received any intelligence of him." A famous instance of the use of this structure for comic effect is “The House that Jack Built.