Heron, I Googled Camassia bulbs, and they didn't look very big. You should take a look.

Hmm, interesting, my encyclopaedia says to plant these 4 inches deep and 2/3 inches apart.

I have just replanted about 200 of these. There are three species, Cc. cuisickii:lechtlinii and esculenta. So C. esculenta (the N American natives Quamash and thus edible) is the smallest bulb and needs to be planted about 3 inches deep. Obviously the plant is not that tall either, about 18 inches. The other two are much bigger bulbs and much taller plants so they need to be planted a little deeper and further apart.
They are prairie plants, so they like the same sort of conditions as F. meleagris, ie. damp meadow.
When suited they increase really well. Some of the balls of bulbs I dug up recently had over 100 bulbs in them, from a single original planting.
They are easy to grow from seed too, even if they do take a while to reach flowering size.
There are white versions as well as purple to go with the original blue.

My Dr Hessayon 'The Bulb Expert' say 4" deep and 6" apart 'you makes your choice' Heron! They like wet and heavy soil (but not water logged) prefering to be left undisturbed under trees or grassland and need lots of water in dry conditions.
Sorry OB we posted at the same time.

Thankyou Owdboggy for what has to be the definitive answer. I fully understand now. I must say that even my Quamash has a tiny bulb for an 18" flower. I'll space them as you say and look forward to a nice Spring display. I'll put some in pots too as I have about 70 bulbs. Thanks to all for your help.

The Quamash bulbs are fairly small, say a big crocus corm size. And it is the whole plant which is about 18 inches not the flower stem. If you think about a Bluebell, which is what C.esculenta looks like, that has a fairly small bulb and an 18 inches flower spike.

Thank you Owdboggy I'll bear that in mind when planting. Good thing you pointed it out really as I was under the impression that mine were much taller like some other varieties.