Magazine  of  the  School  of  Agriculture. 
nothing  to  men  so  familiar  with  all  mechanical 
work  as  these  visitors,  and  therefore  nothing 
arrested  their  attention,  till  they  came  to  the 
viewer,  a highly  skilled  workman,  whose  business 
it  was  to  view  the  barrels  in  order  to  test  their 
straightness.  This  he  did  by  looking  through 
them  at  a pane  of  glass  in  a window  opposite. 
The  upper  part  of  the  pane  was  blackened  down 
to  a line  of  perfect  straightness.  By  directing 
the  barrel  on  this  line  it  was  reflected  on  the 
sides  of  the  brightly  polished  bore  of  the  barrel, 
the  upper  half  of  which  was  thrown  into  shade 
and  divided  from  the  lower  and  fully  illumined 
half  by  the  reflection  of  the  line  on  the  pane. 
Now,  in  looking  through  the  barrel,  its  whole 
length  was  foreshortened  into  a space  of  about 
half  an  inch  on  each  side,  and  therefore 
any  crookedness,  however  slight,  was  magnified 
and  made  perceptible  to  the  experienced  eye  of 
the  viewer,  who  corrected  such  errors  as  he 
discovered  by  delivering  one  or  more  blows  of  a 
wooden  mallet  on  the  barrel,  as  it  lay  on  a wooden 
anvil.  Corrections  so  made  for  Mr.  Whitworth's 
special  information  seemed  to  be  very  effective, 
but  he  remarked  that  those  blows  dislocated  the 
molecular  structure  of  the  metal,  and  were,  beside, 
but  partially  effective. 
It  would  be  beside  my  present  purpose  to  des- 
cribe all  the  exhaustive  experiments  that  were 
carried  on  in  the  shed  at  Rusholme,  500  yards 
in  length,  with  all  appliances  and  apparatus,  and 
it  would  take  up  too  much  time.  Suffice  it  to 
say,  that  when  twenty  of  the  new  Whitworth 
rifles  were  produced  at  the  Wimbledon  meeting, 
and  when  Her  Majesty,  on  being  asked  to  inau- 
gurate the  occasion  by  firing  the  first  shot, 
electrified  Lord  Elcho  by  asking  if  she  should  be 
certain  to  hit  the  bull's  ey°.  Mr.  Whitworth’s  reply 
was  well-known.  “Tell  her  Majesty  she  shall  hit 
the  bull’s  eye ! ” He  accordingly  laid  the  gun 
and  Her  Majesty  fired  the  shot  and  hit  the  bull's 
eye  within  half  an  inch  of  the  centre.  Here  is 
one  of  the  greatest  triumphs  of  purely  technical 
skill  on  record.  Let  the  technical  student  mark 
the  preliminary  care  observed  in  the  prdcis — the 
exhaustive  trials — the  sound  reasoning — the  inti- 
mate knowledge  of  the  behaviour  and  character- 
istics of  the  metals— -and  the  perfect  command 
of  constructive  resource  which  this  inventor 
possessed,  and  he  will  then  understand  the  secret 
of  that  remarkable  success.  Failure  was  barred 
out  at  every  turn  of  the  exhaustive  research. 
There  is  a mine  of  lessons  for  the  technical  student 
in  that  pregnant  example  of  mechanical  skill 
and  research. 
The  Dext  illustration  I take  is  one  of  those  rare 
instances,  to  which  allusion  has  already  been 
made  of  an  invention  produced  in  maturity  at  its 
birth.  It  is  beautiful  in  its  simplicity  and  success. 
A certain  dock  gate,  of  ponderous  dimensions, 
that  had  to  be  opened  once  a day,  required  the 
power  of  300  horses  engine  to  open  it  ; but,  as 
the  work  only  required  the  service  of  the  engine 
for  a few  minutes  daily,  Mr.  (now  Lord)  Arm- 
strong devised  a better  plan.  He  erected  a tower 
with  a cistern  at  the  top,  of  a height  to  give 
the  requisite  head  of  water.  He  then  employed 
a small  engine  to  pump  water  into  the  cistern. 
It  had  all  day  for  its  work,  and  when  the  gate 
had  to  be  opened  the  whole  accumulated  contents 
of  the  reservoir  were  brought  to  bear  on  the  work. 
| Thus  a 10  or  20  horse  engine  was  made  to  do 
I the  work  of  one  of  300.  Similarly,  when  a 
| number  of  cranes  were  all  actuated  by  one  engine 
j it  was  often  brought  up  to  a stand,  when  two 
or  more  cranes  were  simultaneously,  but  the 
inconvenience  was  simply  remedied  by  a hydraulic. 
Even  if  all  the  cranes  happened  to  be  at  work 
simultaneously,  there  were  no  stoppage,  but  only 
a heavier  drain,  for  the  time,  on  the  supply  of 
water  in  the  cistern. 
Now  this  same  inventor,  so  successful  in  the 
work  just  mentioned,  and  who  has  since  been 
so  distinguished  by  others  of  equal  value,  failed 
in  his  next  invention.  The  first  Armstrong  gun 
had  a multigrooved  bore  and  a lead  coated  pro- 
jectile. The  lead  was  intended  to  be  forced  into 
the  grooves  by  the  explosion,  and  to  give  the 
projectile  the  necessary  axial  rotation,  to  insure 
the  accuracy  of  its  flight.  For  this  purpose  it 
proved  to  be  too  weak  ; and  the  angle  of  the 
rifling  had  to  be  reduced  below  the  most  effective 
one.  Even  then,  the  lead  and  the  iron  had  no 
cohesion,  and  being  of  very  different  specific  gra- 
vities, they  often  parted  company  in  flight.  If  I 
am  not  mistaken,  a battery  of  these  guns  was  taken, 
into  the  field  and  misbehaved.  That  form  of  gun. 
was  therefore  abandoned,  and  it  is  now  cited  to- 
show  the  importance  to  an  inventor  of  a perfect 
knowledge  of  the  character,  strength,  and  beha- 
viour of  the  materials  he  uses.  A lesson  is  also 
contained  in  this  example  of  a lack  of  technical 
knowledge,  even  in  an  eminent  technist,  and  of 
the  need  there  is  for  special  examination  of  the 
materials  that  an  inventor  purposes  employing 
for  a new  purpose. 
Whilst  on  the  subject  of  material  I may  adduce 
in  illustration  a most  important  invention,  which 
turns  entirely  upon  the  special  application  of  a 
new  material.  Many  attempts  had  been  made, 
unsuccessfully,  to  construct  a cable  for  submarine 
telegraphy,  until  guttapercha  was  tried,  and  that 
material  solved  the  problem  successfully  and  per- 
manently. The  first  account  of  guttapercha  was 
in  a French  periodical,  La  Technologist e,  about 
1838.  It  was  there  described  as  somewhat  resem- 
bling caoutchouc,  but  wanting  in  the  elasticity 
that  gave  that  substance  its  chief  value.  It  was 
said  to  be  suitable  for  moulding  into  picture  frames 
and  such  like  purposes  ! How  little  could  the 
writer  of  that  paragraph  have  imagined  the  in- 
calculable importance  it  would  come  to  possess 
and  the  revolution  that  would  be  wrought  by  its 
agency.  Here  is  a lesson  to  the  Technical  student, 
of  the  importance  of  an  intimate  acquaintance 
with  materials  of  every  kind,  and  their  properties. 
The  success  or  failure  of  the  greatest  invention 
may,  as  we  have  seen,  be  determined  by  the  use  of 
a material  suitable  to  a particular  purpose. 
It  has  already  been  stated  that  the  great  major- 
ity of  inventions  are  of  a progressive  character  : 
beginning  with  a comparatively  crude  idea,  and 
improved  upon  by  successive  steps,  and  in  many 
cases  reaching  maturity  by  contributions  from 
many  inventors.  From  the  great  mass  of  illustra- 
tions that  might  be  adduced  of  inventions  of  this 
kind,  I select  a few  only.  First  on  the  list  are 
printing  and  photography , which  will  be  treated 
together,  because  of  the  contrast  they  afford  of 
the  slow  development  of  the  former,  owing  to  se- 
crecy observed  by  its  inventors,  compared  with 
the  rapid  progress  of  the  latter,  under  the  modern 
