More manual

Added section on chests.  Fixed another stray British spelling.
Backslashed literal underscores to avoid them being interpreted as
emphasis markup.

manual.md

@@ -20,7 +20,7 @@ to (but actually don't) have their own manuals.
 Recipes for constructable items in technic are generally not guessable,
 and are also not specifically documented here.  You should use a
 craft guide mod to look up the recipes in-game.  For the best possible
-guidance, use the unified_inventory mod, with which technic registers
+guidance, use the unified\_inventory mod, with which technic registers
 its specialised recipe types.
 
 ore
@@ -242,8 +242,8 @@ more than one of the input item: the quantity required is part of
 the recipe.  Centrifuging is only performed by a single machine type,
 the MV (electrically-powered) centrifuge.
 
-Currently, centrifuging recipes don't appear in the unified_inventory
+Currently, centrifuging recipes don't appear in the unified\_inventory
-craft guide, because unified_inventory can't yet handle recipes with
+craft guide, because unified\_inventory can't yet handle recipes with
 multiple outputs.
 
 Generally, centrifuging separates the input item into constituent
@@ -352,7 +352,7 @@ to 2.1%), and intermediate properties: moderately hard and also tough,
 somewhat resistant to corrosion.  In real life it is now used for most
 of the purposes previously satisfied by wrought iron and many of those
 of cast iron, but has historically been especially important for its
-use in swords, armour, skyscrapers, large bridges, and machines.
+use in swords, armor, skyscrapers, large bridges, and machines.
 
 In real-life history, the first form of iron to be refined was
 wrought iron, which is nearly pure iron, having low carbon content.
@@ -450,6 +450,58 @@ latex lump producing one lump of rubber.  If you have an extractor,
 however, the latex is better processed there: each latex lump will
 produce three lumps of rubber.
 
+chests
+------
+
+The technic mod replaces the basic Minetest game's single type of
+chest with a range of chests that have different sizes and features.
+The chest types are identified by the materials from which they are made;
+the better chests are made from more exotic materials.  The chest types
+form a linear sequence, each being (with one exception noted below)
+strictly more powerful than the preceding one.  The sequence begins with
+the wooden chest from the basic game, and each later chest type is built
+by upgrading a chest of the preceding type.  The chest types are:
+
+1.  wooden chest: 8×4 (32) slots
+2.  iron chest: 9×5 (45) slots
+3.  copper chest: 12×5 (60) slots
+4.  silver chest: 12×6 (72) slots
+5.  gold chest: 15×6 (90) slots
+6.  mithril chest: 15×6 (90) slots
+
+The iron and later chests have the ability to sort their contents,
+when commanded by a button in their interaction forms.  Item types are
+sorted in the same order used in the unified\_inventory craft guide.
+The copper and later chests also have an auto-sorting facility that can
+be enabled from the interaction form.  An auto-sorting chest automatically
+sorts its contents whenever a player closes the chest.  The contents will
+then usually be in a sorted state when the chest is opened, but may not
+be if pneumatic tubes have operated on the chest while it was closed,
+or if two players have the chest open simultaneously.
+
+The silver and gold chests, but not the mithril chest, have a built-in
+sign-like capability.  They can be given a textual label, which will
+be visible when hovering over the chest.  The gold chest, but again not
+the mithril chest, can be further labelled with a colored patch that is
+visible from a moderate distance.
+
+The mithril chest is currently an exception to the upgrading system.
+It has only as many inventory slots as the preceding (gold) type, and has
+fewer of the features.  It has no feature that other chests don't have:
+it is strictly weaker than the gold chest.  It is planned that in the
+future it will acquire some unique features, but for now the only reason
+to use it is aesthetic.
+
+The size of the largest chests is dictated by the maximum size
+of interaction form that the game engine can successfully display.
+If in the future the engine becomes capable of handling larger forms,
+by scaling them to fit the screen, the sequence of chest sizes will
+likely be revised.
+
+As with the chest of the basic Minetest game, each chest type comes
+in both locked and unlocked flavors.  All of the chests work with the
+pneumatic tubes of the pipeworks mod.
+
 electrical power
 ----------------
 
@@ -531,4 +583,3 @@ This manual needs to be extended with sections on:
 *   radioactivity
 *   frames
 *   templates
-*   chests