12 A. Gray — Botanical Necrology of 1885. 



approximations. They are indeed sufficiently startling, to 

 make us inclined to proceed with caution ; but, speaking with 

 the reserves indicated by the conditions referred to, I may say 

 that we have every reason to believe that the minimum wave- 

 length assignable to the minimum ordinate of the heat curve, in 

 the spectrum of a source whose temperature varies from 100° to 

 0° Centigrade, is a little less than 5/i and a little over 6/u and that 

 these may be indefinitely greater. This refers, it will be remarked, 

 only to the position of the maximum ordinate, while the extreme 

 portions of the curve measured on (corresponding: to an index of 

 T-15) have probably at least three times this wave-length. I shall 

 be better understood, perhaps, if I say that some of the heat radi- 

 ated by the soil has probably a wave-length of over 150,000 of 

 Angstrom's scale, or about twenty times the wave-length of the 

 lowest visible line in the solar spectrum, as known to Fraun- 

 hofer. 



These investigations are still going forward, and I hope soon 

 to give more exact values. But I have presented the present 

 ones, though imperfect, because they give us at least some 

 knowledge of a region of which we are at present quite ignor- 

 ant, and because they are thus I think of some interest both to 

 the physicist and to the astronomer. To the physicist, as show- 

 ing that the wave-lengths which Newton measured to the ^-.-jnnr 

 of an inch are so far from being the limits of nature's scale, that 

 the existence of measurable wave-lengths of something greater 

 than TjyoVo" °f an ^ ncn ^ s rendered at least highly probable. To 

 the astronomer, because we find that the heat radiated from the 

 soil is of an almost totally different quality from thai which is 

 received from the sun, so that the important processes by which 

 the high surface temperature of the planet are maintained, can 

 now be investigated with, we may hope, fruitful results in con- 

 nection with the researches here described. 



I should not close this preliminary account without stating 

 that I have in these observations been throughout and at every 

 stage, indebted to Messrs. F. W. Very and J. E. Keeler of this 

 Observatory, for a collaboration without which it could, not 

 have appeared in its present form. 



Art. II. —Botanical Necrology of 1885 ; by Asa Gray. 



Charles Wright died on the 11th of August, at Wethers- 

 field, Conn., at the home where he was born on the 29th of 

 October, 1811, and where the early as well as the later years 

 of his life were passed. He received his education in the 

 grammar school of his native village and at Yale College, 



