One of the main features of a proper marmalade is that it contains a lot of pectin that is fluid when the product is still hot from cooking, but forms a gel as it cools down.

However, that gel consists of a sponge of chain-like pectin molecules, soaked in liquid syrup. When the tin is opened the syrup fills the sponge pretty nearly exactly, because the sponge formed from the molecules dispersed evenly through the syrup in whatever concentration the recipe had produced. The whole mix fills the can completely, and if you skimmed your marmalade from the top instead of digging great, vulgar holes in it, that is how the marmalade would continue to be. 

But if you in all your brutal callousness tear hollows into the delicate structure, quarrying it, quarrying it, I say! then the fluid syrup from the higher levels of sponge weeps and seeps into the lower levels of the quarries.

Before you start feeling too guilty though, you can rely on marmalade to turn the other cheek most forgivingly, especially on hot buttered toast. But don't trust it! It is just biding its time to drip on your best shirt and smear your table and floor, or if you are at a hotel, to humiliate you by making you look boorish in the eyes of your guests, hosts, or clients and colleagues. Can't find the bosses' paper? Isnt that it sticking to the seat of your trousers?

Who wrote that rubbish? Can't be me, surely? Must be getting late!