chart = {
const width=400, height=600;
const svg = d3.select(DOM.svg(width, height))
var projection = d3.geoMercator()
.fitExtent([[20, 20], [width, height]], ferries);
var path = d3.geoPath()
.projection(projection);
svg.append('g').selectAll('path')
.data(ferries.features)
.enter().append('path')
.attr('d', path)
.style('fill', 'white')
.style('stroke', '#ccc')
return svg.node()
}