These are naturally most active on the side which is directly exposed to the sun, whence the appearance of the immense glowing envelopes the wolf of wall street 2013 french bdrip x264 aymo surround the nucleus on the sunward side. Among the particles of hydro-carbon, and perhaps solid carbon in the state of fine dust, which are thus set free there will be many whose size is within the critical limit which enables the light-waves from the sun to drive them away. Clouds of such particles, then, will stream off behind the advancing comet, producing the appearance of a tail. This accounts for the fact that the tails of comets are always directed away from the sun, and it also explains the varying forms of the tails and the extraordinary changes that they undergo.