8 
IOWA ACADEMY OF SCIENCES 
expresses it, led to various assumptions, the prevalence of which were 
serious obstacles to the initiation of any attempt to arrive at better con- 
clusions. Thus Pliny, Gessner, in the sixteenth century, Caesalpinus in 
the seventeenth and even Buffcn in the eighteenth, denied the fixity 
of form of crystals. Nicholas Steno in 1669 published the statement that 
tho the sides of the hexagonal crystal may vary the angles are not 
changed. This dictum, tho not accepted by all, as we have seen, became 
the basis of much patient observation on the part of many. Linnaeus 
first attempted to make the crystalline form the basis for the arrangement 
of minerals in groups, but was not successful in his plan. However, 
Rome ‘de Lisle, in reading the works of Linnaeus, found suggestions that 
led to his giving to the form of crystals his devoted study thru a wide 
range of application. By his efforts and those of tiauy a little later, 
crystallography was definitely founded as a means of determining min- 
erals apart from chemistry. The part of Rome ’de Lisle seems to have 
been to prepare the way by patient industry in investigation of details 
for the establishment by Hauy of the principles of crystallography upon 
such a sure foundation that they have been recognized and employed ever 
since by all those who have continued the work. To him is given the 
credit of maintaining the importance of cleavage and the consequent 
explanation of the derivation of secondary from primary forms by means 
of the decrements of the successive layers of integral molecules; “the 
mathematical deduction of the dimensions and proportions of these secon- 
dary forms; the invention of a notation to express them; the examin&- 
tion of the whole mineral kingdom in accordance with these views; and 
the production of a work in which they are explained with singular 
clearness and vivacity.” His industry and skill command the admiration 
of all who have become acquainted with the contributions which he has 
made to the evolution of crystallography. Some of his devices and 
deductions have been superseded by the results of later investigations, 
but even they served a valuable purpose in becoming the vehicles for 
the safe carriage of facts which were necessary to the successful deter- 
mination of the better systems of those who could thus profit by the labors 
of this truly remarkable pioneer in mineralogy. It is true that he had 
the results of the labors of the painstaking and enthusiastic Rome ‘de 
Lisle and others by which to profit, but his, nevertheless, is the unique 
virtue of having used them in such a manner as to have wrought them 
into a consistent and acceptable system that in its essential features con- 
tinues in force up to the present time. 
Later progress in crystallography has consisted largely in increasing 
the accuracy of angle measurements and in adding to our knowledge of 
derived forms. Wollaston made the first of these more readily possible 
by his invention of the reflecting goniometer by which the angles of very 
minute faces could be measured with great accuracy. Two other English- 
men, Phillips and Brooke, made diligent use of this instrument in secur- 
ing exact measurements of the angles of a large number of minerals, the 
results of which were published for the benefit of students of the 
science. , 
