Jump starting a car

[interele]

I was reading my cars manual and it says to jump start, connect the + of the battery from the good car to the + terminal of the battery and the - from the good car to the engine block NOT the - terminal of the battery. It is very specific about this ... why ?

Ta

M

[bigboots]

Some batterys car give off vapours from the acid and a spark can ignite the gasses, connecting the jump leads may cause a spark so best do it away from the battery, i have seen many a good battery explode and a few bonnets ruined by acid

[Panic Button]

I don't know the precise technical details, but it is something to do with preventing power surges which can damage electrical components in the car.

[TonyBeeeee]

Mmmmmm well I could go with bigboots answer to some extent but the others seem a little exotic.
I believe you connect to the engine itself to take any resistance of the battery negative lead to the engine out of the circuit. The starter is bolted to the engine so connecting to a good solid place on the engine gives a better current flow to the starter at a time when the donor car is having to supply lots of current trying to charge a very flat battery as well as turn the starter over.