The  greater  portion  of  the  information  relating  to  the  design
and  improvement  of  the  gas  engine  during  the  period  previous
to  any  extensive  commercial  use  is  obtained  from  the  records  of
the  English,  French  and  American  patent  offices.  "These  records
have  the  advantage  over  other  publications  of  being  definitely
dated  and  of  concisely  and  accurately  describing  the  machine
and  its  mode  of  operation.
The  first  internal  combustion  engine  described  in  the  jjatcnt
records  was  patented  by  Robert  Street  in  England  on  the  7th
of  May,  1794.  It  consists  of  a  motor  cylinder,  with  a  piston,  the
bottom  of  which  is  heated  tiy  fire.  The  patent  shows  a  pump
driven  by  a  lever.  The  fuel  is  described  as  a  small  quantity  of
tar  or  turpentine  which  is  projected  onto  the  hot  part  of  the
cylinder  so  that  the  liquid  is  instantly  converted  into  an  inflam-
mable vapor.  The  raising  of  the  piston  by  means  of  a  lever  sucks
in  external  air  and  also  flame  for  ignition,  which  causes  the  ex-
plosion. The  details  as  described  are  crude,  but  the  principle  of
operation  is  the  same  as  in  the  Lenoir  engine  which  was  patent<  d
in  1860.
