IDEAS TO BE PUBLISHED 373 
Another letter to Harvey (February 3, 1857) strongly 
repeats this appeal against the natural depreciation of his 
own famihar store of knowledge, and insists on man's duty 
of giving his formed ideas to the world. 
I am quite prepared for what you say of your work, it 
was always my case on first venturing, nevertheless you 
have done a great deal already and will soon fall into the 
way of it. A few steady weeks at Systematic Botany in 
the Herb, wondrously renovates and reinvigorates one I 
find, and when weary of desultory head work, I find the 
Herb, a great relief. 
As to your pubhcations I would urge you to think now 
of putting together some of your ideas and facts on wider 
branches than purely descriptive. I think that this becomes 
a duty after a certain time of life with those who keep 
such subjects before them — too much of our dear bought 
experience dies with us, and the pursuit of careful descriptive 
Botany rather renders us too timid about striking out into 
generahties that are the product of years of insensibly gained 
ideas. I express myself abominably and vmte as I think, 
but I am myself urged on all hands to treat some branches 
of Botany in a larger manner, and as soon as I have completed 
my rough hsts of Indian and of Austrahan plants I intend 
to make them the data on which to establish some attempts 
to estimate accurately the relations of numbers of genera 
and species in given areas with climate and elevation, the 
relations numerical of genera to orders, of number of species 
in globe, etc., etc., in short to bring to book upon absolute 
data (tolerable as far as they go) certain principles now 
vaguely enunciated on no fixed data at all. This you could 
do for Southern Algae and connect their migration with 
ocean currents and temp, of Ocean, not in detail, nor upon 
exact data, but upon fair data, and be they good or bad you 
are the only one capable of doing it, and it will take any other 
man many years to come up to your capability and oppor- 
tunity. Heaven knows I dread my subject and feel enough 
my own incompetence, but the work wants doing, nobody 
else has the opportunity, and it is in my position of life as 
clearly my duty as any moral obhgation can well be. Others 
can and will work up species, and I have no right to withhold 
VOL. I 2 b 
