Fade transparent .png's on top of each other on clicking link
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I am creating a 650x 610px historical railway map and would like to start with a blank map, then fade in transparent .png layers containing just a fragment of the railway, one on top of the other, building up to an image of the whole network.  There would be a list of the dates the network was extended to click and make that bit of line appear. Easily done using solid images, but very slow and there are 31 images. I couldn't find any forum queries about this anywhere.  Please could anyone help? 