The Dangerous Book for Boys. Conn Iggulden

this process turns the bones into rock – and they become known as fossils, a slowly created cast of an animal that died hundreds of millions of years ago. Other fossils are formed when dying animals fall into peat bogs or are covered in sand. As each new sedimentary layer takes millions of years to form, we can judge the age of the fossils from their depth. You can travel in time, in fact, if you have a spade. You can reach Roman times in just six or seven feet down in some places. To reach levels millions of years ago, you’ll need to find a cliff where the layers are already revealed – like Lyme Regis and Charmouth in Dorset or the Lake District in Cumbria.

      Those sea animals can move a long way in the time since they were swimming in dark oceans! Geological action can raise great plates of the earth so that what were undersea fossils can be found at the peak of a mountain or in a desert that was once a valley on the sea floor.

      In parts of New Zealand, you can see the fossilised remains of ancient prehistoric forests in visible black bands on the seashore. This particular compressed material is coal and it burns extremely well as fuel. Oil too is a fossil. It is formed in pockets, under great pressure, from animals and plants that lived three hundred million years ago. It is without a doubt the most useful substance we have ever found – everything plastic comes from oil, as well as petrol for our planes and cars.

      By studying fossilised plants and animals, we can take a glimpse at a world that has otherwise vanished. It is a narrow view and the information is nowhere near as complete as we would like, but our understanding improves with every new find.

      Even the commonest fossils can be fascinating. Hold a piece of flint up to the light and see creatures that last crawled before man came out of the caves – before Nelson, before William the Conqueror, before Moses. It fires the imagination. Here are some of the classic forms of fossils.

      Ammonite. A shelled sea creature that died out at the KT boundary 65 million years ago (see Dinosaurs). Sizes vary enormously, but they can be attractively coloured.

      Trilobite. These are also a fairly common find, though the rock must usually be split to see them. Fossil hunters carry small hammers to tap away at samples of rock.

      Sea urchin. Fossilised sea urchins and simple organisms like starfish are all very well, but remnants of woolly mammoths have been found in the south of England, as well as remnants of Jurassic period great carnivores and herbivores. However, you are likely to find a few ammonites on the Dorset coast in a single afternoon, while a Jurassic skeleton would be the find of a lifetime. That said, if you don’t look, you won’t find.

       Building a Treehouse

      LET’S BE BLUNT. Building a decent treehouse is really hard. It takes something like sixty man-hours start to finish and costs more than a hundred pounds in wood and materials. In other words, it’s a job for dads. You could spend the same amount on a games console and a few games, but the treehouse won’t go out of date – and is healthier, frankly. We are well aware of the satisfaction gained from nailing bits of wood to a tree, but for something that looks right, is strong and safe and will last more than just a few months, you need a bit more than that.

      Along with a canoe or a small sailing dinghy, a treehouse is still one of the best things you could possibly have. It’s worth the effort, the sweat, the cost, even the blood if whoever builds it is careless with power tools. It is a thing of beauty. It really should have a skull and crossbones on it somewhere, as well.

      You will need

       Thirty 6-inch (15 cm) coach screws with heavy square washers.

       Eight 8-inch (20 cm) coach screws with washers.

       Thirty-two 4-inch (10 cm) coach screws with washers.

       4 × 3 inch beams – at least 16 ft, but better to get 20 ft (6 m).

       2 × 6 inch (5 × 15 cm) pine planking – 64 ft (19.5 m).

       2 × 4 timber for roof joists and walls – 32 ft + 152 ft (10 m + 46 m): 184 ft (56 m).

       Pine decking to cover the area of the platform – 49 sq ft (4.5 sq m).

       Pine decking for the ladder – 27 sq ft (2.5 sq m).

       Jigsaw power tool, electric drill, rip saw. (Preferably an electric table saw.)

       Spirit level.

       Large drill bits of 14, 16 and 18 mm.

       Stepladder and a long ladder.

       Safety rope.

       Bag of clout nails and a hammer.

       ‘Shiplap’ planking – enough to cover four half walls with a total area of 84 sq ft (7.8 sq m) Add in approximately 49 sq ft (4.5 sq m) for the roof.

       Ratchet spanner with a set of heads to tighten the coach screws.

       Chisel to cut trenches for the trapdoor hinges. Two hinges.

       Four eyebolts that can be screwed into the trunk.

       Cloth bag for trap-door counterweight.

      To build the platform, you need some 2 × 6 inch (5 × 15 cm) pine planking, available from any large wood supplier. Our base was 7 ft by 7 ft (2.1 m × 2.1 m) and that worked out as eight 7 ft (2.1 m) lengths, with one more for bracers. Altogether: 64 ft (19.5 m) of 2 × 6.

      Most dads will be concerned with making this as safe as possible. You really don’t want something this heavy to fall down with children in it. Wherever possible, we went for huge overkill with materials, working on the principle that ‘in the event of nuclear war, this treehouse would remain standing’.

      Choose your tree and check if the treehouse will overlook a neighbour’s garden. If it does and they object, the local council could ask you to take it down again. Choose the height of the base from the ground. This will depend in part on the age of the children, but we put ours eight feet up. Higher ones are more impressive, of course, but are harder to make. If the ground is soft, use a board to stop the feet of the ladders from sinking in.

      THE PLATFORM

      The coach screws need to have holes pre-drilled, so make sure you have a suitable drill bit and a long enough extension lead to reach the tree. We ended up using three leads attached to each other and a double socket on the end. For a previous job, we had attached a table saw to an old table and it proved extremely useful to be able to cut wood as required.

      Build the platform as shown in the diagrams below. Use the safety rope to support the planks until they are secure, putting the rope over a higher branch and tying it off when they are in position. Do not try and walk on the platform before it is supported at each corner. For it to drop, it would have to sheer off a number of steel coach screws, but the turning force of someone standing on a corner is immense and could be disastrous. Supporting the platform is technically the hardest part of the job.

      1. (2 × 6) planks. 7ft long. Held by three six inch coach screws. Not to scale

      2.