46.  International   Definitions    and    Descriptions    of   Cloud
Forms. — The  international  definitions  and  descriptions  of  the
10  types  of  cloud  forms*  are  now  given.     Those  which  follow
are  those  appearing  in  the  "  Observer's  Handbook"  issued  by
the    Meteorological   Office,    London,    1919    edition.      In   that
publication  the  translation   into  English  has   been   altered  in
certain  respects  from  that  which  appears  in  the  English  version
of  the  introduction  to  the  "  International  Cloud  Atlas  "  in  order
to  represent  more  closely  the  original  French.     The  abbrevia-
tions in  brackets  after  the  names  of  the  clouds  are  the  contractions
agreed  upon  internationally,  and  no  others  should  be  used.
"  (1)  tCurus  (Ci.).— Detached  clouds  of  deli-
cate appearance,  fibrous  (threadlike)  structure
and  feather-like  form,  generally  white  in  colour.
Cirrus  clouds  take  the  most  varied  shapes,  such  as  isolated
tufts  of  hair,  i.e.,  thin  filaments  on  a  blue  sky,  branched
filaments  in  feathery  form,  straight  or  curved  filaments
ending  in  tufts  (called  cirrus  uncinus),  and  others.
Occasionally  cirrus  clouds  are  arranged  in  bands,  which
traverse  part  of  the  sky  as  arcs  of  great  circles,  and  as  an
effect  of  perspective  appear  to  converge  at  a  point  on  the
horizon,  and  at  the  opposite  point  also  if  they  are
sufficiently  extended.  Cirro-stratus  and  cirro-cumulus
also  are  sometimes  similarly  arranged  in  long  bands.
"  (2)  ^Cirro-Stratus  (Ci.-St.).  — A  thin  sheet
of  whitish-cloud ;  sometimes  covering  the  sky
completely  and  merely  giving  it  a  milky
appearance;  it  is  then  called  cirro-nebula  or
cirrus  haze;  at  other  times  presenting  more

*  "  Atlas  International  des  Nuages  "  (The  International  Cloud  Atlas).
