30 REPORT OF THE SECRETARY. 
extended series of experiments, however, has been that which relates 
to the condition of the air, and the mode of ventilation of the United 
States Capitol. This subject was referred by Mr. Thomas U. Walter, 
the architect of the Capitol, to the Secretary of this Institution. 
The plan of the investigation having been determined, the experi- 
ments have principally been made by Dr, Wetherill. The result of 
this investigation, it is believed, will not only throw additional light 
on the points for which it was instituted, but also form an interesting 
addition to the subject of ventilation. The work in the laboratory, 
also by Dr. Wetherill, comprised various researches upon subjects of 
chemical science. Of these, three, viz.: ‘‘On the nature of the so- 
called ammonium amalgam;’’ “On the crystallization of sulphur;’’ and 
‘¢QOn the crystalline nature of glass,’’ will be published shortly in one 
of the scientific journals of the country. The means for carrying on 
physical research at the Institution have been materially diminished, 
on account of the destruction by fire of the very valuable collection 
of physical apparatus. Fortunately the conflagration did not extend 
to the laboratory, and consequently the chemical apparatus was pre- 
served. 
Collections of specimens of natural history, &c.—The work of making 
collections of specimens of natural history has been prosecuted as in 
previous years. A very large collection of mammals, birds, eggs, 
&c., made in the northern part of British America in 1863, princi- 
pally by the officers of the Hudson’s Bay Company, has arrived at 
Fort Garry, and is expected soon to be received in Washington. 
Collections have also been received from Labrador, Puget’s sound, 
and from various parts of the United States, Central America, 
Mexico, and the West Indies, a detailed account of which is given in 
the annexed report of Professor Baird. Advantage has been taken 
of every exploring expedition which has been sent out by govern- 
ment, and in many cases of the assistance offered by officers of the 
army, particularly of the medical department, for adding new mate- 
rials or duplicate specimens to the collections. The great object, as 
has been frequently stated before, of this work, is to obtain the ma- 
terials for an extended knowledge of the natural history of this con- 
tinent, and to furnish ‘illustrations of type specimens to museums, 
colleges, and other educational establishments. 
The whole number of specimens catalogued during the last twelve 
years is upwards of 100,000, and including duplicates, the whole 
number collected will amount to five times that amount. 
